Browse Source

extract from latest chrome (v55), resolve #8

wayou 4 years ago
parent
commit
f5659df799

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assets/default_100_percent/100-disabled.png


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assets/default_100_percent/100-error-offline.png


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assets/default_100_percent/100-offline-sprite.png


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assets/default_200_percent/200-disabled.png


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assets/default_200_percent/200-error-offline.png


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assets/default_200_percent/200-offline-sprite.png


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index.html


+ 2708 - 0
index.js

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+// Copyright (c) 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+(function () {
+    'use strict';
+    /**
+     * T-Rex runner.
+     * @param {string} outerContainerId Outer containing element id.
+     * @param {Object} opt_config
+     * @constructor
+     * @export
+     */
+    function Runner(outerContainerId, opt_config) {
+        // Singleton
+        if (Runner.instance_) {
+            return Runner.instance_;
+        }
+        Runner.instance_ = this;
+
+        this.outerContainerEl = document.querySelector(outerContainerId);
+        this.containerEl = null;
+        this.snackbarEl = null;
+        this.detailsButton = this.outerContainerEl.querySelector('#details-button');
+
+        this.config = opt_config || Runner.config;
+
+        this.dimensions = Runner.defaultDimensions;
+
+        this.canvas = null;
+        this.canvasCtx = null;
+
+        this.tRex = null;
+
+        this.distanceMeter = null;
+        this.distanceRan = 0;
+
+        this.highestScore = 0;
+
+        this.time = 0;
+        this.runningTime = 0;
+        this.msPerFrame = 1000 / FPS;
+        this.currentSpeed = this.config.SPEED;
+
+        this.obstacles = [];
+
+        this.activated = false; // Whether the easter egg has been activated.
+        this.playing = false; // Whether the game is currently in play state.
+        this.crashed = false;
+        this.paused = false;
+        this.inverted = false;
+        this.invertTimer = 0;
+        this.resizeTimerId_ = null;
+
+        this.playCount = 0;
+
+        // Sound FX.
+        this.audioBuffer = null;
+        this.soundFx = {};
+
+        // Global web audio context for playing sounds.
+        this.audioContext = null;
+
+        // Images.
+        this.images = {};
+        this.imagesLoaded = 0;
+
+        if (this.isDisabled()) {
+            this.setupDisabledRunner();
+        } else {
+            this.loadImages();
+        }
+    }
+    window['Runner'] = Runner;
+
+
+    /**
+     * Default game width.
+     * @const
+     */
+    var DEFAULT_WIDTH = 600;
+
+    /**
+     * Frames per second.
+     * @const
+     */
+    var FPS = 60;
+
+    /** @const */
+    var IS_HIDPI = window.devicePixelRatio > 1;
+
+    /** @const */
+    var IS_IOS = /iPad|iPhone|iPod/.test(window.navigator.platform);
+
+    /** @const */
+    var IS_MOBILE = /Android/.test(window.navigator.userAgent) || IS_IOS;
+
+    /** @const */
+    var IS_TOUCH_ENABLED = 'ontouchstart' in window;
+
+    /**
+     * Default game configuration.
+     * @enum {number}
+     */
+    Runner.config = {
+        ACCELERATION: 0.001,
+        BG_CLOUD_SPEED: 0.2,
+        BOTTOM_PAD: 10,
+        CLEAR_TIME: 3000,
+        CLOUD_FREQUENCY: 0.5,
+        GAMEOVER_CLEAR_TIME: 750,
+        GAP_COEFFICIENT: 0.6,
+        GRAVITY: 0.6,
+        INITIAL_JUMP_VELOCITY: 12,
+        INVERT_FADE_DURATION: 12000,
+        INVERT_DISTANCE: 700,
+        MAX_BLINK_COUNT: 3,
+        MAX_CLOUDS: 6,
+        MAX_OBSTACLE_LENGTH: 3,
+        MAX_OBSTACLE_DUPLICATION: 2,
+        MAX_SPEED: 13,
+        MIN_JUMP_HEIGHT: 35,
+        MOBILE_SPEED_COEFFICIENT: 1.2,
+        RESOURCE_TEMPLATE_ID: 'audio-resources',
+        SPEED: 6,
+        SPEED_DROP_COEFFICIENT: 3
+    };
+
+
+    /**
+     * Default dimensions.
+     * @enum {string}
+     */
+    Runner.defaultDimensions = {
+        WIDTH: DEFAULT_WIDTH,
+        HEIGHT: 150
+    };
+
+
+    /**
+     * CSS class names.
+     * @enum {string}
+     */
+    Runner.classes = {
+        CANVAS: 'runner-canvas',
+        CONTAINER: 'runner-container',
+        CRASHED: 'crashed',
+        ICON: 'icon-offline',
+        INVERTED: 'inverted',
+        SNACKBAR: 'snackbar',
+        SNACKBAR_SHOW: 'snackbar-show',
+        TOUCH_CONTROLLER: 'controller'
+    };
+
+
+    /**
+     * Sprite definition layout of the spritesheet.
+     * @enum {Object}
+     */
+    Runner.spriteDefinition = {
+        LDPI: {
+            CACTUS_LARGE: { x: 332, y: 2 },
+            CACTUS_SMALL: { x: 228, y: 2 },
+            CLOUD: { x: 86, y: 2 },
+            HORIZON: { x: 2, y: 54 },
+            MOON: { x: 484, y: 2 },
+            PTERODACTYL: { x: 134, y: 2 },
+            RESTART: { x: 2, y: 2 },
+            TEXT_SPRITE: { x: 655, y: 2 },
+            TREX: { x: 848, y: 2 },
+            STAR: { x: 645, y: 2 }
+        },
+        HDPI: {
+            CACTUS_LARGE: { x: 652, y: 2 },
+            CACTUS_SMALL: { x: 446, y: 2 },
+            CLOUD: { x: 166, y: 2 },
+            HORIZON: { x: 2, y: 104 },
+            MOON: { x: 954, y: 2 },
+            PTERODACTYL: { x: 260, y: 2 },
+            RESTART: { x: 2, y: 2 },
+            TEXT_SPRITE: { x: 1294, y: 2 },
+            TREX: { x: 1678, y: 2 },
+            STAR: { x: 1276, y: 2 }
+        }
+    };
+
+
+    /**
+     * Sound FX. Reference to the ID of the audio tag on interstitial page.
+     * @enum {string}
+     */
+    Runner.sounds = {
+        BUTTON_PRESS: 'offline-sound-press',
+        HIT: 'offline-sound-hit',
+        SCORE: 'offline-sound-reached'
+    };
+
+
+    /**
+     * Key code mapping.
+     * @enum {Object}
+     */
+    Runner.keycodes = {
+        JUMP: { '38': 1, '32': 1 },  // Up, spacebar
+        DUCK: { '40': 1 },  // Down
+        RESTART: { '13': 1 }  // Enter
+    };
+
+
+    /**
+     * Runner event names.
+     * @enum {string}
+     */
+    Runner.events = {
+        ANIM_END: 'webkitAnimationEnd',
+        CLICK: 'click',
+        KEYDOWN: 'keydown',
+        KEYUP: 'keyup',
+        MOUSEDOWN: 'mousedown',
+        MOUSEUP: 'mouseup',
+        RESIZE: 'resize',
+        TOUCHEND: 'touchend',
+        TOUCHSTART: 'touchstart',
+        VISIBILITY: 'visibilitychange',
+        BLUR: 'blur',
+        FOCUS: 'focus',
+        LOAD: 'load'
+    };
+
+
+    Runner.prototype = {
+        /**
+         * Whether the easter egg has been disabled. CrOS enterprise enrolled devices.
+         * @return {boolean}
+         */
+        isDisabled: function () {
+            // return loadTimeData && loadTimeData.valueExists('disabledEasterEgg');
+            return false;
+        },
+
+        /**
+         * For disabled instances, set up a snackbar with the disabled message.
+         */
+        setupDisabledRunner: function () {
+            this.containerEl = document.createElement('div');
+            this.containerEl.className = Runner.classes.SNACKBAR;
+            this.containerEl.textContent = loadTimeData.getValue('disabledEasterEgg');
+            this.outerContainerEl.appendChild(this.containerEl);
+
+            // Show notification when the activation key is pressed.
+            document.addEventListener(Runner.events.KEYDOWN, function (e) {
+                if (Runner.keycodes.JUMP[e.keyCode]) {
+                    this.containerEl.classList.add(Runner.classes.SNACKBAR_SHOW);
+                    document.querySelector('.icon').classList.add('icon-disabled');
+                }
+            }.bind(this));
+        },
+
+        /**
+         * Setting individual settings for debugging.
+         * @param {string} setting
+         * @param {*} value
+         */
+        updateConfigSetting: function (setting, value) {
+            if (setting in this.config && value != undefined) {
+                this.config[setting] = value;
+
+                switch (setting) {
+                    case 'GRAVITY':
+                    case 'MIN_JUMP_HEIGHT':
+                    case 'SPEED_DROP_COEFFICIENT':
+                        this.tRex.config[setting] = value;
+                        break;
+                    case 'INITIAL_JUMP_VELOCITY':
+                        this.tRex.setJumpVelocity(value);
+                        break;
+                    case 'SPEED':
+                        this.setSpeed(value);
+                        break;
+                }
+            }
+        },
+
+        /**
+         * Cache the appropriate image sprite from the page and get the sprite sheet
+         * definition.
+         */
+        loadImages: function () {
+            if (IS_HIDPI) {
+                Runner.imageSprite = document.getElementById('offline-resources-2x');
+                this.spriteDef = Runner.spriteDefinition.HDPI;
+            } else {
+                Runner.imageSprite = document.getElementById('offline-resources-1x');
+                this.spriteDef = Runner.spriteDefinition.LDPI;
+            }
+
+            if (Runner.imageSprite.complete) {
+                this.init();
+            } else {
+                // If the images are not yet loaded, add a listener.
+                Runner.imageSprite.addEventListener(Runner.events.LOAD,
+                    this.init.bind(this));
+            }
+        },
+
+        /**
+         * Load and decode base 64 encoded sounds.
+         */
+        loadSounds: function () {
+            if (!IS_IOS) {
+                this.audioContext = new AudioContext();
+
+                var resourceTemplate =
+                    document.getElementById(this.config.RESOURCE_TEMPLATE_ID).content;
+
+                for (var sound in Runner.sounds) {
+                    var soundSrc =
+                        resourceTemplate.getElementById(Runner.sounds[sound]).src;
+                    soundSrc = soundSrc.substr(soundSrc.indexOf(',') + 1);
+                    var buffer = decodeBase64ToArrayBuffer(soundSrc);
+
+                    // Async, so no guarantee of order in array.
+                    this.audioContext.decodeAudioData(buffer, function (index, audioData) {
+                        this.soundFx[index] = audioData;
+                    }.bind(this, sound));
+                }
+            }
+        },
+
+        /**
+         * Sets the game speed. Adjust the speed accordingly if on a smaller screen.
+         * @param {number} opt_speed
+         */
+        setSpeed: function (opt_speed) {
+            var speed = opt_speed || this.currentSpeed;
+
+            // Reduce the speed on smaller mobile screens.
+            if (this.dimensions.WIDTH < DEFAULT_WIDTH) {
+                var mobileSpeed = speed * this.dimensions.WIDTH / DEFAULT_WIDTH *
+                    this.config.MOBILE_SPEED_COEFFICIENT;
+                this.currentSpeed = mobileSpeed > speed ? speed : mobileSpeed;
+            } else if (opt_speed) {
+                this.currentSpeed = opt_speed;
+            }
+        },
+
+        /**
+         * Game initialiser.
+         */
+        init: function () {
+            // Hide the static icon.
+            document.querySelector('.' + Runner.classes.ICON).style.visibility =
+                'hidden';
+
+            this.adjustDimensions();
+            this.setSpeed();
+
+            this.containerEl = document.createElement('div');
+            this.containerEl.className = Runner.classes.CONTAINER;
+
+            // Player canvas container.
+            this.canvas = createCanvas(this.containerEl, this.dimensions.WIDTH,
+                this.dimensions.HEIGHT, Runner.classes.PLAYER);
+
+            this.canvasCtx = this.canvas.getContext('2d');
+            this.canvasCtx.fillStyle = '#f7f7f7';
+            this.canvasCtx.fill();
+            Runner.updateCanvasScaling(this.canvas);
+
+            // Horizon contains clouds, obstacles and the ground.
+            this.horizon = new Horizon(this.canvas, this.spriteDef, this.dimensions,
+                this.config.GAP_COEFFICIENT);
+
+            // Distance meter
+            this.distanceMeter = new DistanceMeter(this.canvas,
+                this.spriteDef.TEXT_SPRITE, this.dimensions.WIDTH);
+
+            // Draw t-rex
+            this.tRex = new Trex(this.canvas, this.spriteDef.TREX);
+
+            this.outerContainerEl.appendChild(this.containerEl);
+
+            if (IS_MOBILE) {
+                this.createTouchController();
+            }
+
+            this.startListening();
+            this.update();
+
+            window.addEventListener(Runner.events.RESIZE,
+                this.debounceResize.bind(this));
+        },
+
+        /**
+         * Create the touch controller. A div that covers whole screen.
+         */
+        createTouchController: function () {
+            this.touchController = document.createElement('div');
+            this.touchController.className = Runner.classes.TOUCH_CONTROLLER;
+        },
+
+        /**
+         * Debounce the resize event.
+         */
+        debounceResize: function () {
+            if (!this.resizeTimerId_) {
+                this.resizeTimerId_ =
+                    setInterval(this.adjustDimensions.bind(this), 250);
+            }
+        },
+
+        /**
+         * Adjust game space dimensions on resize.
+         */
+        adjustDimensions: function () {
+            clearInterval(this.resizeTimerId_);
+            this.resizeTimerId_ = null;
+
+            var boxStyles = window.getComputedStyle(this.outerContainerEl);
+            var padding = Number(boxStyles.paddingLeft.substr(0,
+                boxStyles.paddingLeft.length - 2));
+
+            this.dimensions.WIDTH = this.outerContainerEl.offsetWidth - padding * 2;
+
+            // Redraw the elements back onto the canvas.
+            if (this.canvas) {
+                this.canvas.width = this.dimensions.WIDTH;
+                this.canvas.height = this.dimensions.HEIGHT;
+
+                Runner.updateCanvasScaling(this.canvas);
+
+                this.distanceMeter.calcXPos(this.dimensions.WIDTH);
+                this.clearCanvas();
+                this.horizon.update(0, 0, true);
+                this.tRex.update(0);
+
+                // Outer container and distance meter.
+                if (this.playing || this.crashed || this.paused) {
+                    this.containerEl.style.width = this.dimensions.WIDTH + 'px';
+                    this.containerEl.style.height = this.dimensions.HEIGHT + 'px';
+                    this.distanceMeter.update(0, Math.ceil(this.distanceRan));
+                    this.stop();
+                } else {
+                    this.tRex.draw(0, 0);
+                }
+
+                // Game over panel.
+                if (this.crashed && this.gameOverPanel) {
+                    this.gameOverPanel.updateDimensions(this.dimensions.WIDTH);
+                    this.gameOverPanel.draw();
+                }
+            }
+        },
+
+        /**
+         * Play the game intro.
+         * Canvas container width expands out to the full width.
+         */
+        playIntro: function () {
+            if (!this.activated && !this.crashed) {
+                this.playingIntro = true;
+                this.tRex.playingIntro = true;
+
+                // CSS animation definition.
+                var keyframes = '@-webkit-keyframes intro { ' +
+                    'from { width:' + Trex.config.WIDTH + 'px }' +
+                    'to { width: ' + this.dimensions.WIDTH + 'px }' +
+                    '}';
+                document.styleSheets[0].insertRule(keyframes, 0);
+
+                this.containerEl.addEventListener(Runner.events.ANIM_END,
+                    this.startGame.bind(this));
+
+                this.containerEl.style.webkitAnimation = 'intro .4s ease-out 1 both';
+                this.containerEl.style.width = this.dimensions.WIDTH + 'px';
+
+                if (this.touchController) {
+                    this.outerContainerEl.appendChild(this.touchController);
+                }
+                this.playing = true;
+                this.activated = true;
+            } else if (this.crashed) {
+                this.restart();
+            }
+        },
+
+
+        /**
+         * Update the game status to started.
+         */
+        startGame: function () {
+            this.runningTime = 0;
+            this.playingIntro = false;
+            this.tRex.playingIntro = false;
+            this.containerEl.style.webkitAnimation = '';
+            this.playCount++;
+
+            // Handle tabbing off the page. Pause the current game.
+            document.addEventListener(Runner.events.VISIBILITY,
+                this.onVisibilityChange.bind(this));
+
+            window.addEventListener(Runner.events.BLUR,
+                this.onVisibilityChange.bind(this));
+
+            window.addEventListener(Runner.events.FOCUS,
+                this.onVisibilityChange.bind(this));
+        },
+
+        clearCanvas: function () {
+            this.canvasCtx.clearRect(0, 0, this.dimensions.WIDTH,
+                this.dimensions.HEIGHT);
+        },
+
+        /**
+         * Update the game frame and schedules the next one.
+         */
+        update: function () {
+            this.updatePending = false;
+
+            var now = getTimeStamp();
+            var deltaTime = now - (this.time || now);
+            this.time = now;
+
+            if (this.playing) {
+                this.clearCanvas();
+
+                if (this.tRex.jumping) {
+                    this.tRex.updateJump(deltaTime);
+                }
+
+                this.runningTime += deltaTime;
+                var hasObstacles = this.runningTime > this.config.CLEAR_TIME;
+
+                // First jump triggers the intro.
+                if (this.tRex.jumpCount == 1 && !this.playingIntro) {
+                    this.playIntro();
+                }
+
+                // The horizon doesn't move until the intro is over.
+                if (this.playingIntro) {
+                    this.horizon.update(0, this.currentSpeed, hasObstacles);
+                } else {
+                    deltaTime = !this.activated ? 0 : deltaTime;
+                    this.horizon.update(deltaTime, this.currentSpeed, hasObstacles,
+                        this.inverted);
+                }
+
+                // Check for collisions.
+                var collision = hasObstacles &&
+                    checkForCollision(this.horizon.obstacles[0], this.tRex);
+
+                if (!collision) {
+                    this.distanceRan += this.currentSpeed * deltaTime / this.msPerFrame;
+
+                    if (this.currentSpeed < this.config.MAX_SPEED) {
+                        this.currentSpeed += this.config.ACCELERATION;
+                    }
+                } else {
+                    this.gameOver();
+                }
+
+                var playAchievementSound = this.distanceMeter.update(deltaTime,
+                    Math.ceil(this.distanceRan));
+
+                if (playAchievementSound) {
+                    this.playSound(this.soundFx.SCORE);
+                }
+
+                // Night mode.
+                if (this.invertTimer > this.config.INVERT_FADE_DURATION) {
+                    this.invertTimer = 0;
+                    this.invertTrigger = false;
+                    this.invert();
+                } else if (this.invertTimer) {
+                    this.invertTimer += deltaTime;
+                } else {
+                    var actualDistance =
+                        this.distanceMeter.getActualDistance(Math.ceil(this.distanceRan));
+
+                    if (actualDistance > 0) {
+                        this.invertTrigger = !(actualDistance %
+                            this.config.INVERT_DISTANCE);
+
+                        if (this.invertTrigger && this.invertTimer === 0) {
+                            this.invertTimer += deltaTime;
+                            this.invert();
+                        }
+                    }
+                }
+            }
+
+            if (this.playing || (!this.activated &&
+                this.tRex.blinkCount < Runner.config.MAX_BLINK_COUNT)) {
+                this.tRex.update(deltaTime);
+                this.scheduleNextUpdate();
+            }
+        },
+
+        /**
+         * Event handler.
+         */
+        handleEvent: function (e) {
+            return (function (evtType, events) {
+                switch (evtType) {
+                    case events.KEYDOWN:
+                    case events.TOUCHSTART:
+                    case events.MOUSEDOWN:
+                        this.onKeyDown(e);
+                        break;
+                    case events.KEYUP:
+                    case events.TOUCHEND:
+                    case events.MOUSEUP:
+                        this.onKeyUp(e);
+                        break;
+                }
+            }.bind(this))(e.type, Runner.events);
+        },
+
+        /**
+         * Bind relevant key / mouse / touch listeners.
+         */
+        startListening: function () {
+            // Keys.
+            document.addEventListener(Runner.events.KEYDOWN, this);
+            document.addEventListener(Runner.events.KEYUP, this);
+
+            if (IS_MOBILE) {
+                // Mobile only touch devices.
+                this.touchController.addEventListener(Runner.events.TOUCHSTART, this);
+                this.touchController.addEventListener(Runner.events.TOUCHEND, this);
+                this.containerEl.addEventListener(Runner.events.TOUCHSTART, this);
+            } else {
+                // Mouse.
+                document.addEventListener(Runner.events.MOUSEDOWN, this);
+                document.addEventListener(Runner.events.MOUSEUP, this);
+            }
+        },
+
+        /**
+         * Remove all listeners.
+         */
+        stopListening: function () {
+            document.removeEventListener(Runner.events.KEYDOWN, this);
+            document.removeEventListener(Runner.events.KEYUP, this);
+
+            if (IS_MOBILE) {
+                this.touchController.removeEventListener(Runner.events.TOUCHSTART, this);
+                this.touchController.removeEventListener(Runner.events.TOUCHEND, this);
+                this.containerEl.removeEventListener(Runner.events.TOUCHSTART, this);
+            } else {
+                document.removeEventListener(Runner.events.MOUSEDOWN, this);
+                document.removeEventListener(Runner.events.MOUSEUP, this);
+            }
+        },
+
+        /**
+         * Process keydown.
+         * @param {Event} e
+         */
+        onKeyDown: function (e) {
+            // Prevent native page scrolling whilst tapping on mobile.
+            if (IS_MOBILE && this.playing) {
+                e.preventDefault();
+            }
+
+            if (e.target != this.detailsButton) {
+                if (!this.crashed && (Runner.keycodes.JUMP[e.keyCode] ||
+                    e.type == Runner.events.TOUCHSTART)) {
+                    if (!this.playing) {
+                        this.loadSounds();
+                        this.playing = true;
+                        this.update();
+                        if (window.errorPageController) {
+                            errorPageController.trackEasterEgg();
+                        }
+                    }
+                    //  Play sound effect and jump on starting the game for the first time.
+                    if (!this.tRex.jumping && !this.tRex.ducking) {
+                        this.playSound(this.soundFx.BUTTON_PRESS);
+                        this.tRex.startJump(this.currentSpeed);
+                    }
+                }
+
+                if (this.crashed && e.type == Runner.events.TOUCHSTART &&
+                    e.currentTarget == this.containerEl) {
+                    this.restart();
+                }
+            }
+
+            if (this.playing && !this.crashed && Runner.keycodes.DUCK[e.keyCode]) {
+                e.preventDefault();
+                if (this.tRex.jumping) {
+                    // Speed drop, activated only when jump key is not pressed.
+                    this.tRex.setSpeedDrop();
+                } else if (!this.tRex.jumping && !this.tRex.ducking) {
+                    // Duck.
+                    this.tRex.setDuck(true);
+                }
+            }
+        },
+
+
+        /**
+         * Process key up.
+         * @param {Event} e
+         */
+        onKeyUp: function (e) {
+            var keyCode = String(e.keyCode);
+            var isjumpKey = Runner.keycodes.JUMP[keyCode] ||
+                e.type == Runner.events.TOUCHEND ||
+                e.type == Runner.events.MOUSEDOWN;
+
+            if (this.isRunning() && isjumpKey) {
+                this.tRex.endJump();
+            } else if (Runner.keycodes.DUCK[keyCode]) {
+                this.tRex.speedDrop = false;
+                this.tRex.setDuck(false);
+            } else if (this.crashed) {
+                // Check that enough time has elapsed before allowing jump key to restart.
+                var deltaTime = getTimeStamp() - this.time;
+
+                if (Runner.keycodes.RESTART[keyCode] || this.isLeftClickOnCanvas(e) ||
+                    (deltaTime >= this.config.GAMEOVER_CLEAR_TIME &&
+                        Runner.keycodes.JUMP[keyCode])) {
+                    this.restart();
+                }
+            } else if (this.paused && isjumpKey) {
+                // Reset the jump state
+                this.tRex.reset();
+                this.play();
+            }
+        },
+
+        /**
+         * Returns whether the event was a left click on canvas.
+         * On Windows right click is registered as a click.
+         * @param {Event} e
+         * @return {boolean}
+         */
+        isLeftClickOnCanvas: function (e) {
+            return e.button != null && e.button < 2 &&
+                e.type == Runner.events.MOUSEUP && e.target == this.canvas;
+        },
+
+        /**
+         * RequestAnimationFrame wrapper.
+         */
+        scheduleNextUpdate: function () {
+            if (!this.updatePending) {
+                this.updatePending = true;
+                this.raqId = requestAnimationFrame(this.update.bind(this));
+            }
+        },
+
+        /**
+         * Whether the game is running.
+         * @return {boolean}
+         */
+        isRunning: function () {
+            return !!this.raqId;
+        },
+
+        /**
+         * Game over state.
+         */
+        gameOver: function () {
+            this.playSound(this.soundFx.HIT);
+            vibrate(200);
+
+            this.stop();
+            this.crashed = true;
+            this.distanceMeter.acheivement = false;
+
+            this.tRex.update(100, Trex.status.CRASHED);
+
+            // Game over panel.
+            if (!this.gameOverPanel) {
+                this.gameOverPanel = new GameOverPanel(this.canvas,
+                    this.spriteDef.TEXT_SPRITE, this.spriteDef.RESTART,
+                    this.dimensions);
+            } else {
+                this.gameOverPanel.draw();
+            }
+
+            // Update the high score.
+            if (this.distanceRan > this.highestScore) {
+                this.highestScore = Math.ceil(this.distanceRan);
+                this.distanceMeter.setHighScore(this.highestScore);
+            }
+
+            // Reset the time clock.
+            this.time = getTimeStamp();
+        },
+
+        stop: function () {
+            this.playing = false;
+            this.paused = true;
+            cancelAnimationFrame(this.raqId);
+            this.raqId = 0;
+        },
+
+        play: function () {
+            if (!this.crashed) {
+                this.playing = true;
+                this.paused = false;
+                this.tRex.update(0, Trex.status.RUNNING);
+                this.time = getTimeStamp();
+                this.update();
+            }
+        },
+
+        restart: function () {
+            if (!this.raqId) {
+                this.playCount++;
+                this.runningTime = 0;
+                this.playing = true;
+                this.crashed = false;
+                this.distanceRan = 0;
+                this.setSpeed(this.config.SPEED);
+                this.time = getTimeStamp();
+                this.containerEl.classList.remove(Runner.classes.CRASHED);
+                this.clearCanvas();
+                this.distanceMeter.reset(this.highestScore);
+                this.horizon.reset();
+                this.tRex.reset();
+                this.playSound(this.soundFx.BUTTON_PRESS);
+                this.invert(true);
+                this.update();
+            }
+        },
+
+        /**
+         * Pause the game if the tab is not in focus.
+         */
+        onVisibilityChange: function (e) {
+            if (document.hidden || document.webkitHidden || e.type == 'blur' ||
+                document.visibilityState != 'visible') {
+                this.stop();
+            } else if (!this.crashed) {
+                this.tRex.reset();
+                this.play();
+            }
+        },
+
+        /**
+         * Play a sound.
+         * @param {SoundBuffer} soundBuffer
+         */
+        playSound: function (soundBuffer) {
+            if (soundBuffer) {
+                var sourceNode = this.audioContext.createBufferSource();
+                sourceNode.buffer = soundBuffer;
+                sourceNode.connect(this.audioContext.destination);
+                sourceNode.start(0);
+            }
+        },
+
+        /**
+         * Inverts the current page / canvas colors.
+         * @param {boolean} Whether to reset colors.
+         */
+        invert: function (reset) {
+            if (reset) {
+                document.body.classList.toggle(Runner.classes.INVERTED, false);
+                this.invertTimer = 0;
+                this.inverted = false;
+            } else {
+                this.inverted = document.body.classList.toggle(Runner.classes.INVERTED,
+                    this.invertTrigger);
+            }
+        }
+    };
+
+
+    /**
+     * Updates the canvas size taking into
+     * account the backing store pixel ratio and
+     * the device pixel ratio.
+     *
+     * See article by Paul Lewis:
+     * http://www.html5rocks.com/en/tutorials/canvas/hidpi/
+     *
+     * @param {HTMLCanvasElement} canvas
+     * @param {number} opt_width
+     * @param {number} opt_height
+     * @return {boolean} Whether the canvas was scaled.
+     */
+    Runner.updateCanvasScaling = function (canvas, opt_width, opt_height) {
+        var context = canvas.getContext('2d');
+
+        // Query the various pixel ratios
+        var devicePixelRatio = Math.floor(window.devicePixelRatio) || 1;
+        var backingStoreRatio = Math.floor(context.webkitBackingStorePixelRatio) || 1;
+        var ratio = devicePixelRatio / backingStoreRatio;
+
+        // Upscale the canvas if the two ratios don't match
+        if (devicePixelRatio !== backingStoreRatio) {
+            var oldWidth = opt_width || canvas.width;
+            var oldHeight = opt_height || canvas.height;
+
+            canvas.width = oldWidth * ratio;
+            canvas.height = oldHeight * ratio;
+
+            canvas.style.width = oldWidth + 'px';
+            canvas.style.height = oldHeight + 'px';
+
+            // Scale the context to counter the fact that we've manually scaled
+            // our canvas element.
+            context.scale(ratio, ratio);
+            return true;
+        } else if (devicePixelRatio == 1) {
+            // Reset the canvas width / height. Fixes scaling bug when the page is
+            // zoomed and the devicePixelRatio changes accordingly.
+            canvas.style.width = canvas.width + 'px';
+            canvas.style.height = canvas.height + 'px';
+        }
+        return false;
+    };
+
+
+    /**
+     * Get random number.
+     * @param {number} min
+     * @param {number} max
+     * @param {number}
+     */
+    function getRandomNum(min, max) {
+        return Math.floor(Math.random() * (max - min + 1)) + min;
+    }
+
+
+    /**
+     * Vibrate on mobile devices.
+     * @param {number} duration Duration of the vibration in milliseconds.
+     */
+    function vibrate(duration) {
+        if (IS_MOBILE && window.navigator.vibrate) {
+            window.navigator.vibrate(duration);
+        }
+    }
+
+
+    /**
+     * Create canvas element.
+     * @param {HTMLElement} container Element to append canvas to.
+     * @param {number} width
+     * @param {number} height
+     * @param {string} opt_classname
+     * @return {HTMLCanvasElement}
+     */
+    function createCanvas(container, width, height, opt_classname) {
+        var canvas = document.createElement('canvas');
+        canvas.className = opt_classname ? Runner.classes.CANVAS + ' ' +
+            opt_classname : Runner.classes.CANVAS;
+        canvas.width = width;
+        canvas.height = height;
+        container.appendChild(canvas);
+
+        return canvas;
+    }
+
+
+    /**
+     * Decodes the base 64 audio to ArrayBuffer used by Web Audio.
+     * @param {string} base64String
+     */
+    function decodeBase64ToArrayBuffer(base64String) {
+        var len = (base64String.length / 4) * 3;
+        var str = atob(base64String);
+        var arrayBuffer = new ArrayBuffer(len);
+        var bytes = new Uint8Array(arrayBuffer);
+
+        for (var i = 0; i < len; i++) {
+            bytes[i] = str.charCodeAt(i);
+        }
+        return bytes.buffer;
+    }
+
+
+    /**
+     * Return the current timestamp.
+     * @return {number}
+     */
+    function getTimeStamp() {
+        return IS_IOS ? new Date().getTime() : performance.now();
+    }
+
+
+    //******************************************************************************
+
+
+    /**
+     * Game over panel.
+     * @param {!HTMLCanvasElement} canvas
+     * @param {Object} textImgPos
+     * @param {Object} restartImgPos
+     * @param {!Object} dimensions Canvas dimensions.
+     * @constructor
+     */
+    function GameOverPanel(canvas, textImgPos, restartImgPos, dimensions) {
+        this.canvas = canvas;
+        this.canvasCtx = canvas.getContext('2d');
+        this.canvasDimensions = dimensions;
+        this.textImgPos = textImgPos;
+        this.restartImgPos = restartImgPos;
+        this.draw();
+    };
+
+
+    /**
+     * Dimensions used in the panel.
+     * @enum {number}
+     */
+    GameOverPanel.dimensions = {
+        TEXT_X: 0,
+        TEXT_Y: 13,
+        TEXT_WIDTH: 191,
+        TEXT_HEIGHT: 11,
+        RESTART_WIDTH: 36,
+        RESTART_HEIGHT: 32
+    };
+
+
+    GameOverPanel.prototype = {
+        /**
+         * Update the panel dimensions.
+         * @param {number} width New canvas width.
+         * @param {number} opt_height Optional new canvas height.
+         */
+        updateDimensions: function (width, opt_height) {
+            this.canvasDimensions.WIDTH = width;
+            if (opt_height) {
+                this.canvasDimensions.HEIGHT = opt_height;
+            }
+        },
+
+        /**
+         * Draw the panel.
+         */
+        draw: function () {
+            var dimensions = GameOverPanel.dimensions;
+
+            var centerX = this.canvasDimensions.WIDTH / 2;
+
+            // Game over text.
+            var textSourceX = dimensions.TEXT_X;
+            var textSourceY = dimensions.TEXT_Y;
+            var textSourceWidth = dimensions.TEXT_WIDTH;
+            var textSourceHeight = dimensions.TEXT_HEIGHT;
+
+            var textTargetX = Math.round(centerX - (dimensions.TEXT_WIDTH / 2));
+            var textTargetY = Math.round((this.canvasDimensions.HEIGHT - 25) / 3);
+            var textTargetWidth = dimensions.TEXT_WIDTH;
+            var textTargetHeight = dimensions.TEXT_HEIGHT;
+
+            var restartSourceWidth = dimensions.RESTART_WIDTH;
+            var restartSourceHeight = dimensions.RESTART_HEIGHT;
+            var restartTargetX = centerX - (dimensions.RESTART_WIDTH / 2);
+            var restartTargetY = this.canvasDimensions.HEIGHT / 2;
+
+            if (IS_HIDPI) {
+                textSourceY *= 2;
+                textSourceX *= 2;
+                textSourceWidth *= 2;
+                textSourceHeight *= 2;
+                restartSourceWidth *= 2;
+                restartSourceHeight *= 2;
+            }
+
+            textSourceX += this.textImgPos.x;
+            textSourceY += this.textImgPos.y;
+
+            // Game over text from sprite.
+            this.canvasCtx.drawImage(Runner.imageSprite,
+                textSourceX, textSourceY, textSourceWidth, textSourceHeight,
+                textTargetX, textTargetY, textTargetWidth, textTargetHeight);
+
+            // Restart button.
+            this.canvasCtx.drawImage(Runner.imageSprite,
+                this.restartImgPos.x, this.restartImgPos.y,
+                restartSourceWidth, restartSourceHeight,
+                restartTargetX, restartTargetY, dimensions.RESTART_WIDTH,
+                dimensions.RESTART_HEIGHT);
+        }
+    };
+
+
+    //******************************************************************************
+
+    /**
+     * Check for a collision.
+     * @param {!Obstacle} obstacle
+     * @param {!Trex} tRex T-rex object.
+     * @param {HTMLCanvasContext} opt_canvasCtx Optional canvas context for drawing
+     *    collision boxes.
+     * @return {Array<CollisionBox>}
+     */
+    function checkForCollision(obstacle, tRex, opt_canvasCtx) {
+        var obstacleBoxXPos = Runner.defaultDimensions.WIDTH + obstacle.xPos;
+
+        // Adjustments are made to the bounding box as there is a 1 pixel white
+        // border around the t-rex and obstacles.
+        var tRexBox = new CollisionBox(
+            tRex.xPos + 1,
+            tRex.yPos + 1,
+            tRex.config.WIDTH - 2,
+            tRex.config.HEIGHT - 2);
+
+        var obstacleBox = new CollisionBox(
+            obstacle.xPos + 1,
+            obstacle.yPos + 1,
+            obstacle.typeConfig.width * obstacle.size - 2,
+            obstacle.typeConfig.height - 2);
+
+        // Debug outer box
+        if (opt_canvasCtx) {
+            drawCollisionBoxes(opt_canvasCtx, tRexBox, obstacleBox);
+        }
+
+        // Simple outer bounds check.
+        if (boxCompare(tRexBox, obstacleBox)) {
+            var collisionBoxes = obstacle.collisionBoxes;
+            var tRexCollisionBoxes = tRex.ducking ?
+                Trex.collisionBoxes.DUCKING : Trex.collisionBoxes.RUNNING;
+
+            // Detailed axis aligned box check.
+            for (var t = 0; t < tRexCollisionBoxes.length; t++) {
+                for (var i = 0; i < collisionBoxes.length; i++) {
+                    // Adjust the box to actual positions.
+                    var adjTrexBox =
+                        createAdjustedCollisionBox(tRexCollisionBoxes[t], tRexBox);
+                    var adjObstacleBox =
+                        createAdjustedCollisionBox(collisionBoxes[i], obstacleBox);
+                    var crashed = boxCompare(adjTrexBox, adjObstacleBox);
+
+                    // Draw boxes for debug.
+                    if (opt_canvasCtx) {
+                        drawCollisionBoxes(opt_canvasCtx, adjTrexBox, adjObstacleBox);
+                    }
+
+                    if (crashed) {
+                        return [adjTrexBox, adjObstacleBox];
+                    }
+                }
+            }
+        }
+        return false;
+    };
+
+
+    /**
+     * Adjust the collision box.
+     * @param {!CollisionBox} box The original box.
+     * @param {!CollisionBox} adjustment Adjustment box.
+     * @return {CollisionBox} The adjusted collision box object.
+     */
+    function createAdjustedCollisionBox(box, adjustment) {
+        return new CollisionBox(
+            box.x + adjustment.x,
+            box.y + adjustment.y,
+            box.width,
+            box.height);
+    };
+
+
+    /**
+     * Draw the collision boxes for debug.
+     */
+    function drawCollisionBoxes(canvasCtx, tRexBox, obstacleBox) {
+        canvasCtx.save();
+        canvasCtx.strokeStyle = '#f00';
+        canvasCtx.strokeRect(tRexBox.x, tRexBox.y, tRexBox.width, tRexBox.height);
+
+        canvasCtx.strokeStyle = '#0f0';
+        canvasCtx.strokeRect(obstacleBox.x, obstacleBox.y,
+            obstacleBox.width, obstacleBox.height);
+        canvasCtx.restore();
+    };
+
+
+    /**
+     * Compare two collision boxes for a collision.
+     * @param {CollisionBox} tRexBox
+     * @param {CollisionBox} obstacleBox
+     * @return {boolean} Whether the boxes intersected.
+     */
+    function boxCompare(tRexBox, obstacleBox) {
+        var crashed = false;
+        var tRexBoxX = tRexBox.x;
+        var tRexBoxY = tRexBox.y;
+
+        var obstacleBoxX = obstacleBox.x;
+        var obstacleBoxY = obstacleBox.y;
+
+        // Axis-Aligned Bounding Box method.
+        if (tRexBox.x < obstacleBoxX + obstacleBox.width &&
+            tRexBox.x + tRexBox.width > obstacleBoxX &&
+            tRexBox.y < obstacleBox.y + obstacleBox.height &&
+            tRexBox.height + tRexBox.y > obstacleBox.y) {
+            crashed = true;
+        }
+
+        return crashed;
+    };
+
+
+    //******************************************************************************
+
+    /**
+     * Collision box object.
+     * @param {number} x X position.
+     * @param {number} y Y Position.
+     * @param {number} w Width.
+     * @param {number} h Height.
+     */
+    function CollisionBox(x, y, w, h) {
+        this.x = x;
+        this.y = y;
+        this.width = w;
+        this.height = h;
+    };
+
+
+    //******************************************************************************
+
+    /**
+     * Obstacle.
+     * @param {HTMLCanvasCtx} canvasCtx
+     * @param {Obstacle.type} type
+     * @param {Object} spritePos Obstacle position in sprite.
+     * @param {Object} dimensions
+     * @param {number} gapCoefficient Mutipler in determining the gap.
+     * @param {number} speed
+     * @param {number} opt_xOffset
+     */
+    function Obstacle(canvasCtx, type, spriteImgPos, dimensions,
+        gapCoefficient, speed, opt_xOffset) {
+
+        this.canvasCtx = canvasCtx;
+        this.spritePos = spriteImgPos;
+        this.typeConfig = type;
+        this.gapCoefficient = gapCoefficient;
+        this.size = getRandomNum(1, Obstacle.MAX_OBSTACLE_LENGTH);
+        this.dimensions = dimensions;
+        this.remove = false;
+        this.xPos = dimensions.WIDTH + (opt_xOffset || 0);
+        this.yPos = 0;
+        this.width = 0;
+        this.collisionBoxes = [];
+        this.gap = 0;
+        this.speedOffset = 0;
+
+        // For animated obstacles.
+        this.currentFrame = 0;
+        this.timer = 0;
+
+        this.init(speed);
+    };
+
+    /**
+     * Coefficient for calculating the maximum gap.
+     * @const
+     */
+    Obstacle.MAX_GAP_COEFFICIENT = 1.5;
+
+    /**
+     * Maximum obstacle grouping count.
+     * @const
+     */
+    Obstacle.MAX_OBSTACLE_LENGTH = 3,
+
+
+        Obstacle.prototype = {
+            /**
+             * Initialise the DOM for the obstacle.
+             * @param {number} speed
+             */
+            init: function (speed) {
+                this.cloneCollisionBoxes();
+
+                // Only allow sizing if we're at the right speed.
+                if (this.size > 1 && this.typeConfig.multipleSpeed > speed) {
+                    this.size = 1;
+                }
+
+                this.width = this.typeConfig.width * this.size;
+
+                // Check if obstacle can be positioned at various heights.
+                if (Array.isArray(this.typeConfig.yPos)) {
+                    var yPosConfig = IS_MOBILE ? this.typeConfig.yPosMobile :
+                        this.typeConfig.yPos;
+                    this.yPos = yPosConfig[getRandomNum(0, yPosConfig.length - 1)];
+                } else {
+                    this.yPos = this.typeConfig.yPos;
+                }
+
+                this.draw();
+
+                // Make collision box adjustments,
+                // Central box is adjusted to the size as one box.
+                //      ____        ______        ________
+                //    _|   |-|    _|     |-|    _|       |-|
+                //   | |<->| |   | |<--->| |   | |<----->| |
+                //   | | 1 | |   | |  2  | |   | |   3   | |
+                //   |_|___|_|   |_|_____|_|   |_|_______|_|
+                //
+                if (this.size > 1) {
+                    this.collisionBoxes[1].width = this.width - this.collisionBoxes[0].width -
+                        this.collisionBoxes[2].width;
+                    this.collisionBoxes[2].x = this.width - this.collisionBoxes[2].width;
+                }
+
+                // For obstacles that go at a different speed from the horizon.
+                if (this.typeConfig.speedOffset) {
+                    this.speedOffset = Math.random() > 0.5 ? this.typeConfig.speedOffset :
+                        -this.typeConfig.speedOffset;
+                }
+
+                this.gap = this.getGap(this.gapCoefficient, speed);
+            },
+
+            /**
+             * Draw and crop based on size.
+             */
+            draw: function () {
+                var sourceWidth = this.typeConfig.width;
+                var sourceHeight = this.typeConfig.height;
+
+                if (IS_HIDPI) {
+                    sourceWidth = sourceWidth * 2;
+                    sourceHeight = sourceHeight * 2;
+                }
+
+                // X position in sprite.
+                var sourceX = (sourceWidth * this.size) * (0.5 * (this.size - 1)) +
+                    this.spritePos.x;
+
+                // Animation frames.
+                if (this.currentFrame > 0) {
+                    sourceX += sourceWidth * this.currentFrame;
+                }
+
+                this.canvasCtx.drawImage(Runner.imageSprite,
+                    sourceX, this.spritePos.y,
+                    sourceWidth * this.size, sourceHeight,
+                    this.xPos, this.yPos,
+                    this.typeConfig.width * this.size, this.typeConfig.height);
+            },
+
+            /**
+             * Obstacle frame update.
+             * @param {number} deltaTime
+             * @param {number} speed
+             */
+            update: function (deltaTime, speed) {
+                if (!this.remove) {
+                    if (this.typeConfig.speedOffset) {
+                        speed += this.speedOffset;
+                    }
+                    this.xPos -= Math.floor((speed * FPS / 1000) * deltaTime);
+
+                    // Update frame
+                    if (this.typeConfig.numFrames) {
+                        this.timer += deltaTime;
+                        if (this.timer >= this.typeConfig.frameRate) {
+                            this.currentFrame =
+                                this.currentFrame == this.typeConfig.numFrames - 1 ?
+                                    0 : this.currentFrame + 1;
+                            this.timer = 0;
+                        }
+                    }
+                    this.draw();
+
+                    if (!this.isVisible()) {
+                        this.remove = true;
+                    }
+                }
+            },
+
+            /**
+             * Calculate a random gap size.
+             * - Minimum gap gets wider as speed increses
+             * @param {number} gapCoefficient
+             * @param {number} speed
+             * @return {number} The gap size.
+             */
+            getGap: function (gapCoefficient, speed) {
+                var minGap = Math.round(this.width * speed +
+                    this.typeConfig.minGap * gapCoefficient);
+                var maxGap = Math.round(minGap * Obstacle.MAX_GAP_COEFFICIENT);
+                return getRandomNum(minGap, maxGap);
+            },
+
+            /**
+             * Check if obstacle is visible.
+             * @return {boolean} Whether the obstacle is in the game area.
+             */
+            isVisible: function () {
+                return this.xPos + this.width > 0;
+            },
+
+            /**
+             * Make a copy of the collision boxes, since these will change based on
+             * obstacle type and size.
+             */
+            cloneCollisionBoxes: function () {
+                var collisionBoxes = this.typeConfig.collisionBoxes;
+
+                for (var i = collisionBoxes.length - 1; i >= 0; i--) {
+                    this.collisionBoxes[i] = new CollisionBox(collisionBoxes[i].x,
+                        collisionBoxes[i].y, collisionBoxes[i].width,
+                        collisionBoxes[i].height);
+                }
+            }
+        };
+
+
+    /**
+     * Obstacle definitions.
+     * minGap: minimum pixel space betweeen obstacles.
+     * multipleSpeed: Speed at which multiples are allowed.
+     * speedOffset: speed faster / slower than the horizon.
+     * minSpeed: Minimum speed which the obstacle can make an appearance.
+     */
+    Obstacle.types = [
+        {
+            type: 'CACTUS_SMALL',
+            width: 17,
+            height: 35,
+            yPos: 105,
+            multipleSpeed: 4,
+            minGap: 120,
+            minSpeed: 0,
+            collisionBoxes: [
+                new CollisionBox(0, 7, 5, 27),
+                new CollisionBox(4, 0, 6, 34),
+                new CollisionBox(10, 4, 7, 14)
+            ]
+        },
+        {
+            type: 'CACTUS_LARGE',
+            width: 25,
+            height: 50,
+            yPos: 90,
+            multipleSpeed: 7,
+            minGap: 120,
+            minSpeed: 0,
+            collisionBoxes: [
+                new CollisionBox(0, 12, 7, 38),
+                new CollisionBox(8, 0, 7, 49),
+                new CollisionBox(13, 10, 10, 38)
+            ]
+        },
+        {
+            type: 'PTERODACTYL',
+            width: 46,
+            height: 40,
+            yPos: [100, 75, 50], // Variable height.
+            yPosMobile: [100, 50], // Variable height mobile.
+            multipleSpeed: 999,
+            minSpeed: 8.5,
+            minGap: 150,
+            collisionBoxes: [
+                new CollisionBox(15, 15, 16, 5),
+                new CollisionBox(18, 21, 24, 6),
+                new CollisionBox(2, 14, 4, 3),
+                new CollisionBox(6, 10, 4, 7),
+                new CollisionBox(10, 8, 6, 9)
+            ],
+            numFrames: 2,
+            frameRate: 1000 / 6,
+            speedOffset: .8
+        }
+    ];
+
+
+    //******************************************************************************
+    /**
+     * T-rex game character.
+     * @param {HTMLCanvas} canvas
+     * @param {Object} spritePos Positioning within image sprite.
+     * @constructor
+     */
+    function Trex(canvas, spritePos) {
+        this.canvas = canvas;
+        this.canvasCtx = canvas.getContext('2d');
+        this.spritePos = spritePos;
+        this.xPos = 0;
+        this.yPos = 0;
+        // Position when on the ground.
+        this.groundYPos = 0;
+        this.currentFrame = 0;
+        this.currentAnimFrames = [];
+        this.blinkDelay = 0;
+        this.blinkCount = 0;
+        this.animStartTime = 0;
+        this.timer = 0;
+        this.msPerFrame = 1000 / FPS;
+        this.config = Trex.config;
+        // Current status.
+        this.status = Trex.status.WAITING;
+
+        this.jumping = false;
+        this.ducking = false;
+        this.jumpVelocity = 0;
+        this.reachedMinHeight = false;
+        this.speedDrop = false;
+        this.jumpCount = 0;
+        this.jumpspotX = 0;
+
+        this.init();
+    };
+
+
+    /**
+     * T-rex player config.
+     * @enum {number}
+     */
+    Trex.config = {
+        DROP_VELOCITY: -5,
+        GRAVITY: 0.6,
+        HEIGHT: 47,
+        HEIGHT_DUCK: 25,
+        INIITAL_JUMP_VELOCITY: -10,
+        INTRO_DURATION: 1500,
+        MAX_JUMP_HEIGHT: 30,
+        MIN_JUMP_HEIGHT: 30,
+        SPEED_DROP_COEFFICIENT: 3,
+        SPRITE_WIDTH: 262,
+        START_X_POS: 50,
+        WIDTH: 44,
+        WIDTH_DUCK: 59
+    };
+
+
+    /**
+     * Used in collision detection.
+     * @type {Array<CollisionBox>}
+     */
+    Trex.collisionBoxes = {
+        DUCKING: [
+            new CollisionBox(1, 18, 55, 25)
+        ],
+        RUNNING: [
+            new CollisionBox(22, 0, 17, 16),
+            new CollisionBox(1, 18, 30, 9),
+            new CollisionBox(10, 35, 14, 8),
+            new CollisionBox(1, 24, 29, 5),
+            new CollisionBox(5, 30, 21, 4),
+            new CollisionBox(9, 34, 15, 4)
+        ]
+    };
+
+
+    /**
+     * Animation states.
+     * @enum {string}
+     */
+    Trex.status = {
+        CRASHED: 'CRASHED',
+        DUCKING: 'DUCKING',
+        JUMPING: 'JUMPING',
+        RUNNING: 'RUNNING',
+        WAITING: 'WAITING'
+    };
+
+    /**
+     * Blinking coefficient.
+     * @const
+     */
+    Trex.BLINK_TIMING = 7000;
+
+
+    /**
+     * Animation config for different states.
+     * @enum {Object}
+     */
+    Trex.animFrames = {
+        WAITING: {
+            frames: [44, 0],
+            msPerFrame: 1000 / 3
+        },
+        RUNNING: {
+            frames: [88, 132],
+            msPerFrame: 1000 / 12
+        },
+        CRASHED: {
+            frames: [220],
+            msPerFrame: 1000 / 60
+        },
+        JUMPING: {
+            frames: [0],
+            msPerFrame: 1000 / 60
+        },
+        DUCKING: {
+            frames: [262, 321],
+            msPerFrame: 1000 / 8
+        }
+    };
+
+
+    Trex.prototype = {
+        /**
+         * T-rex player initaliser.
+         * Sets the t-rex to blink at random intervals.
+         */
+        init: function () {
+            this.groundYPos = Runner.defaultDimensions.HEIGHT - this.config.HEIGHT -
+                Runner.config.BOTTOM_PAD;
+            this.yPos = this.groundYPos;
+            this.minJumpHeight = this.groundYPos - this.config.MIN_JUMP_HEIGHT;
+
+            this.draw(0, 0);
+            this.update(0, Trex.status.WAITING);
+        },
+
+        /**
+         * Setter for the jump velocity.
+         * The approriate drop velocity is also set.
+         */
+        setJumpVelocity: function (setting) {
+            this.config.INIITAL_JUMP_VELOCITY = -setting;
+            this.config.DROP_VELOCITY = -setting / 2;
+        },
+
+        /**
+         * Set the animation status.
+         * @param {!number} deltaTime
+         * @param {Trex.status} status Optional status to switch to.
+         */
+        update: function (deltaTime, opt_status) {
+            this.timer += deltaTime;
+
+            // Update the status.
+            if (opt_status) {
+                this.status = opt_status;
+                this.currentFrame = 0;
+                this.msPerFrame = Trex.animFrames[opt_status].msPerFrame;
+                this.currentAnimFrames = Trex.animFrames[opt_status].frames;
+
+                if (opt_status == Trex.status.WAITING) {
+                    this.animStartTime = getTimeStamp();
+                    this.setBlinkDelay();
+                }
+            }
+
+            // Game intro animation, T-rex moves in from the left.
+            if (this.playingIntro && this.xPos < this.config.START_X_POS) {
+                this.xPos += Math.round((this.config.START_X_POS /
+                    this.config.INTRO_DURATION) * deltaTime);
+            }
+
+            if (this.status == Trex.status.WAITING) {
+                this.blink(getTimeStamp());
+            } else {
+                this.draw(this.currentAnimFrames[this.currentFrame], 0);
+            }
+
+            // Update the frame position.
+            if (this.timer >= this.msPerFrame) {
+                this.currentFrame = this.currentFrame ==
+                    this.currentAnimFrames.length - 1 ? 0 : this.currentFrame + 1;
+                this.timer = 0;
+            }
+
+            // Speed drop becomes duck if the down key is still being pressed.
+            if (this.speedDrop && this.yPos == this.groundYPos) {
+                this.speedDrop = false;
+                this.setDuck(true);
+            }
+        },
+
+        /**
+         * Draw the t-rex to a particular position.
+         * @param {number} x
+         * @param {number} y
+         */
+        draw: function (x, y) {
+            var sourceX = x;
+            var sourceY = y;
+            var sourceWidth = this.ducking && this.status != Trex.status.CRASHED ?
+                this.config.WIDTH_DUCK : this.config.WIDTH;
+            var sourceHeight = this.config.HEIGHT;
+
+            if (IS_HIDPI) {
+                sourceX *= 2;
+                sourceY *= 2;
+                sourceWidth *= 2;
+                sourceHeight *= 2;
+            }
+
+            // Adjustments for sprite sheet position.
+            sourceX += this.spritePos.x;
+            sourceY += this.spritePos.y;
+
+            // Ducking.
+            if (this.ducking && this.status != Trex.status.CRASHED) {
+                this.canvasCtx.drawImage(Runner.imageSprite, sourceX, sourceY,
+                    sourceWidth, sourceHeight,
+                    this.xPos, this.yPos,
+                    this.config.WIDTH_DUCK, this.config.HEIGHT);
+            } else {
+                // Crashed whilst ducking. Trex is standing up so needs adjustment.
+                if (this.ducking && this.status == Trex.status.CRASHED) {
+                    this.xPos++;
+                }
+                // Standing / running
+                this.canvasCtx.drawImage(Runner.imageSprite, sourceX, sourceY,
+                    sourceWidth, sourceHeight,
+                    this.xPos, this.yPos,
+                    this.config.WIDTH, this.config.HEIGHT);
+            }
+        },
+
+        /**
+         * Sets a random time for the blink to happen.
+         */
+        setBlinkDelay: function () {
+            this.blinkDelay = Math.ceil(Math.random() * Trex.BLINK_TIMING);
+        },
+
+        /**
+         * Make t-rex blink at random intervals.
+         * @param {number} time Current time in milliseconds.
+         */
+        blink: function (time) {
+            var deltaTime = time - this.animStartTime;
+
+            if (deltaTime >= this.blinkDelay) {
+                this.draw(this.currentAnimFrames[this.currentFrame], 0);
+
+                if (this.currentFrame == 1) {
+                    // Set new random delay to blink.
+                    this.setBlinkDelay();
+                    this.animStartTime = time;
+                    this.blinkCount++;
+                }
+            }
+        },
+
+        /**
+         * Initialise a jump.
+         * @param {number} speed
+         */
+        startJump: function (speed) {
+            if (!this.jumping) {
+                this.update(0, Trex.status.JUMPING);
+                // Tweak the jump velocity based on the speed.
+                this.jumpVelocity = this.config.INIITAL_JUMP_VELOCITY - (speed / 10);
+                this.jumping = true;
+                this.reachedMinHeight = false;
+                this.speedDrop = false;
+            }
+        },
+
+        /**
+         * Jump is complete, falling down.
+         */
+        endJump: function () {
+            if (this.reachedMinHeight &&
+                this.jumpVelocity < this.config.DROP_VELOCITY) {
+                this.jumpVelocity = this.config.DROP_VELOCITY;
+            }
+        },
+
+        /**
+         * Update frame for a jump.
+         * @param {number} deltaTime
+         * @param {number} speed
+         */
+        updateJump: function (deltaTime, speed) {
+            var msPerFrame = Trex.animFrames[this.status].msPerFrame;
+            var framesElapsed = deltaTime / msPerFrame;
+
+            // Speed drop makes Trex fall faster.
+            if (this.speedDrop) {
+                this.yPos += Math.round(this.jumpVelocity *
+                    this.config.SPEED_DROP_COEFFICIENT * framesElapsed);
+            } else {
+                this.yPos += Math.round(this.jumpVelocity * framesElapsed);
+            }
+
+            this.jumpVelocity += this.config.GRAVITY * framesElapsed;
+
+            // Minimum height has been reached.
+            if (this.yPos < this.minJumpHeight || this.speedDrop) {
+                this.reachedMinHeight = true;
+            }
+
+            // Reached max height
+            if (this.yPos < this.config.MAX_JUMP_HEIGHT || this.speedDrop) {
+                this.endJump();
+            }
+
+            // Back down at ground level. Jump completed.
+            if (this.yPos > this.groundYPos) {
+                this.reset();
+                this.jumpCount++;
+            }
+
+            this.update(deltaTime);
+        },
+
+        /**
+         * Set the speed drop. Immediately cancels the current jump.
+         */
+        setSpeedDrop: function () {
+            this.speedDrop = true;
+            this.jumpVelocity = 1;
+        },
+
+        /**
+         * @param {boolean} isDucking.
+         */
+        setDuck: function (isDucking) {
+            if (isDucking && this.status != Trex.status.DUCKING) {
+                this.update(0, Trex.status.DUCKING);
+                this.ducking = true;
+            } else if (this.status == Trex.status.DUCKING) {
+                this.update(0, Trex.status.RUNNING);
+                this.ducking = false;
+            }
+        },
+
+        /**
+         * Reset the t-rex to running at start of game.
+         */
+        reset: function () {
+            this.yPos = this.groundYPos;
+            this.jumpVelocity = 0;
+            this.jumping = false;
+            this.ducking = false;
+            this.update(0, Trex.status.RUNNING);
+            this.midair = false;
+            this.speedDrop = false;
+            this.jumpCount = 0;
+        }
+    };
+
+
+    //******************************************************************************
+
+    /**
+     * Handles displaying the distance meter.
+     * @param {!HTMLCanvasElement} canvas
+     * @param {Object} spritePos Image position in sprite.
+     * @param {number} canvasWidth
+     * @constructor
+     */
+    function DistanceMeter(canvas, spritePos, canvasWidth) {
+        this.canvas = canvas;
+        this.canvasCtx = canvas.getContext('2d');
+        this.image = Runner.imageSprite;
+        this.spritePos = spritePos;
+        this.x = 0;
+        this.y = 5;
+
+        this.currentDistance = 0;
+        this.maxScore = 0;
+        this.highScore = 0;
+        this.container = null;
+
+        this.digits = [];
+        this.acheivement = false;
+        this.defaultString = '';
+        this.flashTimer = 0;
+        this.flashIterations = 0;
+        this.invertTrigger = false;
+
+        this.config = DistanceMeter.config;
+        this.maxScoreUnits = this.config.MAX_DISTANCE_UNITS;
+        this.init(canvasWidth);
+    };
+
+
+    /**
+     * @enum {number}
+     */
+    DistanceMeter.dimensions = {
+        WIDTH: 10,
+        HEIGHT: 13,
+        DEST_WIDTH: 11
+    };
+
+
+    /**
+     * Y positioning of the digits in the sprite sheet.
+     * X position is always 0.
+     * @type {Array<number>}
+     */
+    DistanceMeter.yPos = [0, 13, 27, 40, 53, 67, 80, 93, 107, 120];
+
+
+    /**
+     * Distance meter config.
+     * @enum {number}
+     */
+    DistanceMeter.config = {
+        // Number of digits.
+        MAX_DISTANCE_UNITS: 5,
+
+        // Distance that causes achievement animation.
+        ACHIEVEMENT_DISTANCE: 100,
+
+        // Used for conversion from pixel distance to a scaled unit.
+        COEFFICIENT: 0.025,
+
+        // Flash duration in milliseconds.
+        FLASH_DURATION: 1000 / 4,
+
+        // Flash iterations for achievement animation.
+        FLASH_ITERATIONS: 3
+    };
+
+
+    DistanceMeter.prototype = {
+        /**
+         * Initialise the distance meter to '00000'.
+         * @param {number} width Canvas width in px.
+         */
+        init: function (width) {
+            var maxDistanceStr = '';
+
+            this.calcXPos(width);
+            this.maxScore = this.maxScoreUnits;
+            for (var i = 0; i < this.maxScoreUnits; i++) {
+                this.draw(i, 0);
+                this.defaultString += '0';
+                maxDistanceStr += '9';
+            }
+
+            this.maxScore = parseInt(maxDistanceStr);
+        },
+
+        /**
+         * Calculate the xPos in the canvas.
+         * @param {number} canvasWidth
+         */
+        calcXPos: function (canvasWidth) {
+            this.x = canvasWidth - (DistanceMeter.dimensions.DEST_WIDTH *
+                (this.maxScoreUnits + 1));
+        },
+
+        /**
+         * Draw a digit to canvas.
+         * @param {number} digitPos Position of the digit.
+         * @param {number} value Digit value 0-9.
+         * @param {boolean} opt_highScore Whether drawing the high score.
+         */
+        draw: function (digitPos, value, opt_highScore) {
+            var sourceWidth = DistanceMeter.dimensions.WIDTH;
+            var sourceHeight = DistanceMeter.dimensions.HEIGHT;
+            var sourceX = DistanceMeter.dimensions.WIDTH * value;
+            var sourceY = 0;
+
+            var targetX = digitPos * DistanceMeter.dimensions.DEST_WIDTH;
+            var targetY = this.y;
+            var targetWidth = DistanceMeter.dimensions.WIDTH;
+            var targetHeight = DistanceMeter.dimensions.HEIGHT;
+
+            // For high DPI we 2x source values.
+            if (IS_HIDPI) {
+                sourceWidth *= 2;
+                sourceHeight *= 2;
+                sourceX *= 2;
+            }
+
+            sourceX += this.spritePos.x;
+            sourceY += this.spritePos.y;
+
+            this.canvasCtx.save();
+
+            if (opt_highScore) {
+                // Left of the current score.
+                var highScoreX = this.x - (this.maxScoreUnits * 2) *
+                    DistanceMeter.dimensions.WIDTH;
+                this.canvasCtx.translate(highScoreX, this.y);
+            } else {
+                this.canvasCtx.translate(this.x, this.y);
+            }
+
+            this.canvasCtx.drawImage(this.image, sourceX, sourceY,
+                sourceWidth, sourceHeight,
+                targetX, targetY,
+                targetWidth, targetHeight
+            );
+
+            this.canvasCtx.restore();
+        },
+
+        /**
+         * Covert pixel distance to a 'real' distance.
+         * @param {number} distance Pixel distance ran.
+         * @return {number} The 'real' distance ran.
+         */
+        getActualDistance: function (distance) {
+            return distance ? Math.round(distance * this.config.COEFFICIENT) : 0;
+        },
+
+        /**
+         * Update the distance meter.
+         * @param {number} distance
+         * @param {number} deltaTime
+         * @return {boolean} Whether the acheivement sound fx should be played.
+         */
+        update: function (deltaTime, distance) {
+            var paint = true;
+            var playSound = false;
+
+            if (!this.acheivement) {
+                distance = this.getActualDistance(distance);
+                // Score has gone beyond the initial digit count.
+                if (distance > this.maxScore && this.maxScoreUnits ==
+                    this.config.MAX_DISTANCE_UNITS) {
+                    this.maxScoreUnits++;
+                    this.maxScore = parseInt(this.maxScore + '9');
+                } else {
+                    this.distance = 0;
+                }
+
+                if (distance > 0) {
+                    // Acheivement unlocked
+                    if (distance % this.config.ACHIEVEMENT_DISTANCE == 0) {
+                        // Flash score and play sound.
+                        this.acheivement = true;
+                        this.flashTimer = 0;
+                        playSound = true;
+                    }
+
+                    // Create a string representation of the distance with leading 0.
+                    var distanceStr = (this.defaultString +
+                        distance).substr(-this.maxScoreUnits);
+                    this.digits = distanceStr.split('');
+                } else {
+                    this.digits = this.defaultString.split('');
+                }
+            } else {
+                // Control flashing of the score on reaching acheivement.
+                if (this.flashIterations <= this.config.FLASH_ITERATIONS) {
+                    this.flashTimer += deltaTime;
+
+                    if (this.flashTimer < this.config.FLASH_DURATION) {
+                        paint = false;
+                    } else if (this.flashTimer >
+                        this.config.FLASH_DURATION * 2) {
+                        this.flashTimer = 0;
+                        this.flashIterations++;
+                    }
+                } else {
+                    this.acheivement = false;
+                    this.flashIterations = 0;
+                    this.flashTimer = 0;
+                }
+            }
+
+            // Draw the digits if not flashing.
+            if (paint) {
+                for (var i = this.digits.length - 1; i >= 0; i--) {
+                    this.draw(i, parseInt(this.digits[i]));
+                }
+            }
+
+            this.drawHighScore();
+            return playSound;
+        },
+
+        /**
+         * Draw the high score.
+         */
+        drawHighScore: function () {
+            this.canvasCtx.save();
+            this.canvasCtx.globalAlpha = .8;
+            for (var i = this.highScore.length - 1; i >= 0; i--) {
+                this.draw(i, parseInt(this.highScore[i], 10), true);
+            }
+            this.canvasCtx.restore();
+        },
+
+        /**
+         * Set the highscore as a array string.
+         * Position of char in the sprite: H - 10, I - 11.
+         * @param {number} distance Distance ran in pixels.
+         */
+        setHighScore: function (distance) {
+            distance = this.getActualDistance(distance);
+            var highScoreStr = (this.defaultString +
+                distance).substr(-this.maxScoreUnits);
+
+            this.highScore = ['10', '11', ''].concat(highScoreStr.split(''));
+        },
+
+        /**
+         * Reset the distance meter back to '00000'.
+         */
+        reset: function () {
+            this.update(0);
+            this.acheivement = false;
+        }
+    };
+
+
+    //******************************************************************************
+
+    /**
+     * Cloud background item.
+     * Similar to an obstacle object but without collision boxes.
+     * @param {HTMLCanvasElement} canvas Canvas element.
+     * @param {Object} spritePos Position of image in sprite.
+     * @param {number} containerWidth
+     */
+    function Cloud(canvas, spritePos, containerWidth) {
+        this.canvas = canvas;
+        this.canvasCtx = this.canvas.getContext('2d');
+        this.spritePos = spritePos;
+        this.containerWidth = containerWidth;
+        this.xPos = containerWidth;
+        this.yPos = 0;
+        this.remove = false;
+        this.cloudGap = getRandomNum(Cloud.config.MIN_CLOUD_GAP,
+            Cloud.config.MAX_CLOUD_GAP);
+
+        this.init();
+    };
+
+
+    /**
+     * Cloud object config.
+     * @enum {number}
+     */
+    Cloud.config = {
+        HEIGHT: 14,
+        MAX_CLOUD_GAP: 400,
+        MAX_SKY_LEVEL: 30,
+        MIN_CLOUD_GAP: 100,
+        MIN_SKY_LEVEL: 71,
+        WIDTH: 46
+    };
+
+
+    Cloud.prototype = {
+        /**
+         * Initialise the cloud. Sets the Cloud height.
+         */
+        init: function () {
+            this.yPos = getRandomNum(Cloud.config.MAX_SKY_LEVEL,
+                Cloud.config.MIN_SKY_LEVEL);
+            this.draw();
+        },
+
+        /**
+         * Draw the cloud.
+         */
+        draw: function () {
+            this.canvasCtx.save();
+            var sourceWidth = Cloud.config.WIDTH;
+            var sourceHeight = Cloud.config.HEIGHT;
+
+            if (IS_HIDPI) {
+                sourceWidth = sourceWidth * 2;
+                sourceHeight = sourceHeight * 2;
+            }
+
+            this.canvasCtx.drawImage(Runner.imageSprite, this.spritePos.x,
+                this.spritePos.y,
+                sourceWidth, sourceHeight,
+                this.xPos, this.yPos,
+                Cloud.config.WIDTH, Cloud.config.HEIGHT);
+
+            this.canvasCtx.restore();
+        },
+
+        /**
+         * Update the cloud position.
+         * @param {number} speed
+         */
+        update: function (speed) {
+            if (!this.remove) {
+                this.xPos -= Math.ceil(speed);
+                this.draw();
+
+                // Mark as removeable if no longer in the canvas.
+                if (!this.isVisible()) {
+                    this.remove = true;
+                }
+            }
+        },
+
+        /**
+         * Check if the cloud is visible on the stage.
+         * @return {boolean}
+         */
+        isVisible: function () {
+            return this.xPos + Cloud.config.WIDTH > 0;
+        }
+    };
+
+
+    //******************************************************************************
+
+    /**
+     * Nightmode shows a moon and stars on the horizon.
+     */
+    function NightMode(canvas, spritePos, containerWidth) {
+        this.spritePos = spritePos;
+        this.canvas = canvas;
+        this.canvasCtx = canvas.getContext('2d');
+        this.xPos = containerWidth - 50;
+        this.yPos = 30;
+        this.currentPhase = 0;
+        this.opacity = 0;
+        this.containerWidth = containerWidth;
+        this.stars = [];
+        this.drawStars = false;
+        this.placeStars();
+    };
+
+    /**
+     * @enum {number}
+     */
+    NightMode.config = {
+        FADE_SPEED: 0.035,
+        HEIGHT: 40,
+        MOON_SPEED: 0.25,
+        NUM_STARS: 2,
+        STAR_SIZE: 9,
+        STAR_SPEED: 0.3,
+        STAR_MAX_Y: 70,
+        WIDTH: 20
+    };
+
+    NightMode.phases = [140, 120, 100, 60, 40, 20, 0];
+
+    NightMode.prototype = {
+        /**
+         * Update moving moon, changing phases.
+         * @param {boolean} activated Whether night mode is activated.
+         * @param {number} delta
+         */
+        update: function (activated, delta) {
+            // Moon phase.
+            if (activated && this.opacity == 0) {
+                this.currentPhase++;
+
+                if (this.currentPhase >= NightMode.phases.length) {
+                    this.currentPhase = 0;
+                }
+            }
+
+            // Fade in / out.
+            if (activated && (this.opacity < 1 || this.opacity == 0)) {
+                this.opacity += NightMode.config.FADE_SPEED;
+            } else if (this.opacity > 0) {
+                this.opacity -= NightMode.config.FADE_SPEED;
+            }
+
+            // Set moon positioning.
+            if (this.opacity > 0) {
+                this.xPos = this.updateXPos(this.xPos, NightMode.config.MOON_SPEED);
+
+                // Update stars.
+                if (this.drawStars) {
+                    for (var i = 0; i < NightMode.config.NUM_STARS; i++) {
+                        this.stars[i].x = this.updateXPos(this.stars[i].x,
+                            NightMode.config.STAR_SPEED);
+                    }
+                }
+                this.draw();
+            } else {
+                this.opacity = 0;
+                this.placeStars();
+            }
+            this.drawStars = true;
+        },
+
+        updateXPos: function (currentPos, speed) {
+            if (currentPos < -NightMode.config.WIDTH) {
+                currentPos = this.containerWidth;
+            } else {
+                currentPos -= speed;
+            }
+            return currentPos;
+        },
+
+        draw: function () {
+            var moonSourceWidth = this.currentPhase == 3 ? NightMode.config.WIDTH * 2 :
+                NightMode.config.WIDTH;
+            var moonSourceHeight = NightMode.config.HEIGHT;
+            var moonSourceX = this.spritePos.x + NightMode.phases[this.currentPhase];
+            var moonOutputWidth = moonSourceWidth;
+            var starSize = NightMode.config.STAR_SIZE;
+            var starSourceX = Runner.spriteDefinition.LDPI.STAR.x;
+
+            if (IS_HIDPI) {
+                moonSourceWidth *= 2;
+                moonSourceHeight *= 2;
+                moonSourceX = this.spritePos.x +
+                    (NightMode.phases[this.currentPhase] * 2);
+                starSize *= 2;
+                starSourceX = Runner.spriteDefinition.HDPI.STAR.x;
+            }
+
+            this.canvasCtx.save();
+            this.canvasCtx.globalAlpha = this.opacity;
+
+            // Stars.
+            if (this.drawStars) {
+                for (var i = 0; i < NightMode.config.NUM_STARS; i++) {
+                    this.canvasCtx.drawImage(Runner.imageSprite,
+                        starSourceX, this.stars[i].sourceY, starSize, starSize,
+                        Math.round(this.stars[i].x), this.stars[i].y,
+                        NightMode.config.STAR_SIZE, NightMode.config.STAR_SIZE);
+                }
+            }
+
+            // Moon.
+            this.canvasCtx.drawImage(Runner.imageSprite, moonSourceX,
+                this.spritePos.y, moonSourceWidth, moonSourceHeight,
+                Math.round(this.xPos), this.yPos,
+                moonOutputWidth, NightMode.config.HEIGHT);
+
+            this.canvasCtx.globalAlpha = 1;
+            this.canvasCtx.restore();
+        },
+
+        // Do star placement.
+        placeStars: function () {
+            var segmentSize = Math.round(this.containerWidth /
+                NightMode.config.NUM_STARS);
+
+            for (var i = 0; i < NightMode.config.NUM_STARS; i++) {
+                this.stars[i] = {};
+                this.stars[i].x = getRandomNum(segmentSize * i, segmentSize * (i + 1));
+                this.stars[i].y = getRandomNum(0, NightMode.config.STAR_MAX_Y);
+
+                if (IS_HIDPI) {
+                    this.stars[i].sourceY = Runner.spriteDefinition.HDPI.STAR.y +
+                        NightMode.config.STAR_SIZE * 2 * i;
+                } else {
+                    this.stars[i].sourceY = Runner.spriteDefinition.LDPI.STAR.y +
+                        NightMode.config.STAR_SIZE * i;
+                }
+            }
+        },
+
+        reset: function () {
+            this.currentPhase = 0;
+            this.opacity = 0;
+            this.update(false);
+        }
+
+    };
+
+
+    //******************************************************************************
+
+    /**
+     * Horizon Line.
+     * Consists of two connecting lines. Randomly assigns a flat / bumpy horizon.
+     * @param {HTMLCanvasElement} canvas
+     * @param {Object} spritePos Horizon position in sprite.
+     * @constructor
+     */
+    function HorizonLine(canvas, spritePos) {
+        this.spritePos = spritePos;
+        this.canvas = canvas;
+        this.canvasCtx = canvas.getContext('2d');
+        this.sourceDimensions = {};
+        this.dimensions = HorizonLine.dimensions;
+        this.sourceXPos = [this.spritePos.x, this.spritePos.x +
+            this.dimensions.WIDTH];
+        this.xPos = [];
+        this.yPos = 0;
+        this.bumpThreshold = 0.5;
+
+        this.setSourceDimensions();
+        this.draw();
+    };
+
+
+    /**
+     * Horizon line dimensions.
+     * @enum {number}
+     */
+    HorizonLine.dimensions = {
+        WIDTH: 600,
+        HEIGHT: 12,
+        YPOS: 127
+    };
+
+
+    HorizonLine.prototype = {
+        /**
+         * Set the source dimensions of the horizon line.
+         */
+        setSourceDimensions: function () {
+
+            for (var dimension in HorizonLine.dimensions) {
+                if (IS_HIDPI) {
+                    if (dimension != 'YPOS') {
+                        this.sourceDimensions[dimension] =
+                            HorizonLine.dimensions[dimension] * 2;
+                    }
+                } else {
+                    this.sourceDimensions[dimension] =
+                        HorizonLine.dimensions[dimension];
+                }
+                this.dimensions[dimension] = HorizonLine.dimensions[dimension];
+            }
+
+            this.xPos = [0, HorizonLine.dimensions.WIDTH];
+            this.yPos = HorizonLine.dimensions.YPOS;
+        },
+
+        /**
+         * Return the crop x position of a type.
+         */
+        getRandomType: function () {
+            return Math.random() > this.bumpThreshold ? this.dimensions.WIDTH : 0;
+        },
+
+        /**
+         * Draw the horizon line.
+         */
+        draw: function () {
+            this.canvasCtx.drawImage(Runner.imageSprite, this.sourceXPos[0],
+                this.spritePos.y,
+                this.sourceDimensions.WIDTH, this.sourceDimensions.HEIGHT,
+                this.xPos[0], this.yPos,
+                this.dimensions.WIDTH, this.dimensions.HEIGHT);
+
+            this.canvasCtx.drawImage(Runner.imageSprite, this.sourceXPos[1],
+                this.spritePos.y,
+                this.sourceDimensions.WIDTH, this.sourceDimensions.HEIGHT,
+                this.xPos[1], this.yPos,
+                this.dimensions.WIDTH, this.dimensions.HEIGHT);
+        },
+
+        /**
+         * Update the x position of an indivdual piece of the line.
+         * @param {number} pos Line position.
+         * @param {number} increment
+         */
+        updateXPos: function (pos, increment) {
+            var line1 = pos;
+            var line2 = pos == 0 ? 1 : 0;
+
+            this.xPos[line1] -= increment;
+            this.xPos[line2] = this.xPos[line1] + this.dimensions.WIDTH;
+
+            if (this.xPos[line1] <= -this.dimensions.WIDTH) {
+                this.xPos[line1] += this.dimensions.WIDTH * 2;
+                this.xPos[line2] = this.xPos[line1] - this.dimensions.WIDTH;
+                this.sourceXPos[line1] = this.getRandomType() + this.spritePos.x;
+            }
+        },
+
+        /**
+         * Update the horizon line.
+         * @param {number} deltaTime
+         * @param {number} speed
+         */
+        update: function (deltaTime, speed) {
+            var increment = Math.floor(speed * (FPS / 1000) * deltaTime);
+
+            if (this.xPos[0] <= 0) {
+                this.updateXPos(0, increment);
+            } else {
+                this.updateXPos(1, increment);
+            }
+            this.draw();
+        },
+
+        /**
+         * Reset horizon to the starting position.
+         */
+        reset: function () {
+            this.xPos[0] = 0;
+            this.xPos[1] = HorizonLine.dimensions.WIDTH;
+        }
+    };
+
+
+    //******************************************************************************
+
+    /**
+     * Horizon background class.
+     * @param {HTMLCanvasElement} canvas
+     * @param {Object} spritePos Sprite positioning.
+     * @param {Object} dimensions Canvas dimensions.
+     * @param {number} gapCoefficient
+     * @constructor
+     */
+    function Horizon(canvas, spritePos, dimensions, gapCoefficient) {
+        this.canvas = canvas;
+        this.canvasCtx = this.canvas.getContext('2d');
+        this.config = Horizon.config;
+        this.dimensions = dimensions;
+        this.gapCoefficient = gapCoefficient;
+        this.obstacles = [];
+        this.obstacleHistory = [];
+        this.horizonOffsets = [0, 0];
+        this.cloudFrequency = this.config.CLOUD_FREQUENCY;
+        this.spritePos = spritePos;
+        this.nightMode = null;
+
+        // Cloud
+        this.clouds = [];
+        this.cloudSpeed = this.config.BG_CLOUD_SPEED;
+
+        // Horizon
+        this.horizonLine = null;
+        this.init();
+    };
+
+
+    /**
+     * Horizon config.
+     * @enum {number}
+     */
+    Horizon.config = {
+        BG_CLOUD_SPEED: 0.2,
+        BUMPY_THRESHOLD: .3,
+        CLOUD_FREQUENCY: .5,
+        HORIZON_HEIGHT: 16,
+        MAX_CLOUDS: 6
+    };
+
+
+    Horizon.prototype = {
+        /**
+         * Initialise the horizon. Just add the line and a cloud. No obstacles.
+         */
+        init: function () {
+            this.addCloud();
+            this.horizonLine = new HorizonLine(this.canvas, this.spritePos.HORIZON);
+            this.nightMode = new NightMode(this.canvas, this.spritePos.MOON,
+                this.dimensions.WIDTH);
+        },
+
+        /**
+         * @param {number} deltaTime
+         * @param {number} currentSpeed
+         * @param {boolean} updateObstacles Used as an override to prevent
+         *     the obstacles from being updated / added. This happens in the
+         *     ease in section.
+         * @param {boolean} showNightMode Night mode activated.
+         */
+        update: function (deltaTime, currentSpeed, updateObstacles, showNightMode) {
+            this.runningTime += deltaTime;
+            this.horizonLine.update(deltaTime, currentSpeed);
+            this.nightMode.update(showNightMode);
+            this.updateClouds(deltaTime, currentSpeed);
+
+            if (updateObstacles) {
+                this.updateObstacles(deltaTime, currentSpeed);
+            }
+        },
+
+        /**
+         * Update the cloud positions.
+         * @param {number} deltaTime
+         * @param {number} currentSpeed
+         */
+        updateClouds: function (deltaTime, speed) {
+            var cloudSpeed = this.cloudSpeed / 1000 * deltaTime * speed;
+            var numClouds = this.clouds.length;
+
+            if (numClouds) {
+                for (var i = numClouds - 1; i >= 0; i--) {
+                    this.clouds[i].update(cloudSpeed);
+                }
+
+                var lastCloud = this.clouds[numClouds - 1];
+
+                // Check for adding a new cloud.
+                if (numClouds < this.config.MAX_CLOUDS &&
+                    (this.dimensions.WIDTH - lastCloud.xPos) > lastCloud.cloudGap &&
+                    this.cloudFrequency > Math.random()) {
+                    this.addCloud();
+                }
+
+                // Remove expired clouds.
+                this.clouds = this.clouds.filter(function (obj) {
+                    return !obj.remove;
+                });
+            } else {
+                this.addCloud();
+            }
+        },
+
+        /**
+         * Update the obstacle positions.
+         * @param {number} deltaTime
+         * @param {number} currentSpeed
+         */
+        updateObstacles: function (deltaTime, currentSpeed) {
+            // Obstacles, move to Horizon layer.
+            var updatedObstacles = this.obstacles.slice(0);
+
+            for (var i = 0; i < this.obstacles.length; i++) {
+                var obstacle = this.obstacles[i];
+                obstacle.update(deltaTime, currentSpeed);
+
+                // Clean up existing obstacles.
+                if (obstacle.remove) {
+                    updatedObstacles.shift();
+                }
+            }
+            this.obstacles = updatedObstacles;
+
+            if (this.obstacles.length > 0) {
+                var lastObstacle = this.obstacles[this.obstacles.length - 1];
+
+                if (lastObstacle && !lastObstacle.followingObstacleCreated &&
+                    lastObstacle.isVisible() &&
+                    (lastObstacle.xPos + lastObstacle.width + lastObstacle.gap) <
+                    this.dimensions.WIDTH) {
+                    this.addNewObstacle(currentSpeed);
+                    lastObstacle.followingObstacleCreated = true;
+                }
+            } else {
+                // Create new obstacles.
+                this.addNewObstacle(currentSpeed);
+            }
+        },
+
+        removeFirstObstacle: function () {
+            this.obstacles.shift();
+        },
+
+        /**
+         * Add a new obstacle.
+         * @param {number} currentSpeed
+         */
+        addNewObstacle: function (currentSpeed) {
+            var obstacleTypeIndex = getRandomNum(0, Obstacle.types.length - 1);
+            var obstacleType = Obstacle.types[obstacleTypeIndex];
+
+            // Check for multiples of the same type of obstacle.
+            // Also check obstacle is available at current speed.
+            if (this.duplicateObstacleCheck(obstacleType.type) ||
+                currentSpeed < obstacleType.minSpeed) {
+                this.addNewObstacle(currentSpeed);
+            } else {
+                var obstacleSpritePos = this.spritePos[obstacleType.type];
+
+                this.obstacles.push(new Obstacle(this.canvasCtx, obstacleType,
+                    obstacleSpritePos, this.dimensions,
+                    this.gapCoefficient, currentSpeed, obstacleType.width));
+
+                this.obstacleHistory.unshift(obstacleType.type);
+
+                if (this.obstacleHistory.length > 1) {
+                    this.obstacleHistory.splice(Runner.config.MAX_OBSTACLE_DUPLICATION);
+                }
+            }
+        },
+
+        /**
+         * Returns whether the previous two obstacles are the same as the next one.
+         * Maximum duplication is set in config value MAX_OBSTACLE_DUPLICATION.
+         * @return {boolean}
+         */
+        duplicateObstacleCheck: function (nextObstacleType) {
+            var duplicateCount = 0;
+
+            for (var i = 0; i < this.obstacleHistory.length; i++) {
+                duplicateCount = this.obstacleHistory[i] == nextObstacleType ?
+                    duplicateCount + 1 : 0;
+            }
+            return duplicateCount >= Runner.config.MAX_OBSTACLE_DUPLICATION;
+        },
+
+        /**
+         * Reset the horizon layer.
+         * Remove existing obstacles and reposition the horizon line.
+         */
+        reset: function () {
+            this.obstacles = [];
+            this.horizonLine.reset();
+            this.nightMode.reset();
+        },
+
+        /**
+         * Update the canvas width and scaling.
+         * @param {number} width Canvas width.
+         * @param {number} height Canvas height.
+         */
+        resize: function (width, height) {
+            this.canvas.width = width;
+            this.canvas.height = height;
+        },
+
+        /**
+         * Add a new cloud to the horizon.
+         */
+        addCloud: function () {
+            this.clouds.push(new Cloud(this.canvas, this.spritePos.CLOUD,
+                this.dimensions.WIDTH));
+        }
+    };
+})();
+
+
+function onDocumentLoad() {
+    new Runner('.interstitial-wrapper');
+}
+
+document.addEventListener('DOMContentLoaded', onDocumentLoad);

+ 0 - 2515
js/game.js

@@ -1,2515 +0,0 @@
-// Copyright (c) 2014 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-(function() {
-'use strict';
-/**
- * T-Rex runner.
- * @param {string} outerContainerId Outer containing element id.
- * @param {Object} opt_config
- * @constructor
- * @export
- */
-function Runner(outerContainerId, opt_config) {
-  // Singleton
-  if (Runner.instance_) {
-    return Runner.instance_;
-  }
-  Runner.instance_ = this;
-
-  this.outerContainerEl = document.querySelector(outerContainerId);
-  this.containerEl = null;
-  this.snackbarEl = null;
-  // this.detailsButton = this.outerContainerEl.querySelector('#details-button');
-
-  this.config = opt_config || Runner.config;
-
-  this.dimensions = Runner.defaultDimensions;
-
-  this.canvas = null;
-  this.canvasCtx = null;
-
-  this.tRex = null;
-
-  this.distanceMeter = null;
-  this.distanceRan = 0;
-
-  this.highestScore = 0;
-
-  this.time = 0;
-  this.runningTime = 0;
-  this.msPerFrame = 1000 / FPS;
-  this.currentSpeed = this.config.SPEED;
-
-  this.obstacles = [];
-
-  this.started = false;
-  this.activated = false;
-  this.crashed = false;
-  this.paused = false;
-
-  this.resizeTimerId_ = null;
-
-  this.playCount = 0;
-
-  // Sound FX.
-  this.audioBuffer = null;
-  this.soundFx = {};
-
-  // Global web audio context for playing sounds.
-  this.audioContext = null;
-
-  // Images.
-  this.images = {};
-  this.imagesLoaded = 0;
-
-  // if (this.isDisabled()) {
-  //   this.setupDisabledRunner();
-  // } else {
-    this.loadImages();
-  // }
-
-  this.gamepadPreviousKeyDown = false;
-}
-window['Runner'] = Runner;
-
-
-/**
- * Default game width.
- * @const
- */
-var DEFAULT_WIDTH = 600;
-
-/**
- * Frames per second.
- * @const
- */
-var FPS = 60;
-
-/** @const */
-var IS_HIDPI = window.devicePixelRatio > 1;
-
-/** @const */
-var IS_IOS = window.navigator.userAgent.indexOf('CriOS') > -1 ||
-    window.navigator.userAgent == 'UIWebViewForStaticFileContent';
-
-/** @const */
-var IS_MOBILE = window.navigator.userAgent.indexOf('Mobi') > -1 || IS_IOS;
-
-/** @const */
-var IS_TOUCH_ENABLED = 'ontouchstart' in window;
-
-/**
- * Default game configuration.
- * @enum {number}
- */
-Runner.config = {
-  ACCELERATION: 0.001,
-  BG_CLOUD_SPEED: 0.2,
-  BOTTOM_PAD: 10,
-  CLEAR_TIME: 3000,
-  CLOUD_FREQUENCY: 0.5,
-  GAMEOVER_CLEAR_TIME: 750,
-  GAP_COEFFICIENT: 0.6,
-  GRAVITY: 0.6,
-  INITIAL_JUMP_VELOCITY: 12,
-  MAX_CLOUDS: 6,
-  MAX_OBSTACLE_LENGTH: 3,
-  MAX_OBSTACLE_DUPLICATION: 2,
-  MAX_SPEED: 13,
-  MIN_JUMP_HEIGHT: 35,
-  MOBILE_SPEED_COEFFICIENT: 1.2,
-  RESOURCE_TEMPLATE_ID: 'audio-resources',
-  SPEED: 6,
-  SPEED_DROP_COEFFICIENT: 3
-};
-
-
-/**
- * Default dimensions.
- * @enum {string}
- */
-Runner.defaultDimensions = {
-  WIDTH: DEFAULT_WIDTH,
-  HEIGHT: 150
-};
-
-
-/**
- * CSS class names.
- * @enum {string}
- */
-Runner.classes = {
-  CANVAS: 'runner-canvas',
-  CONTAINER: 'runner-container',
-  CRASHED: 'crashed',
-  ICON: 'icon-offline',
-  SNACKBAR: 'snackbar',
-  SNACKBAR_SHOW: 'snackbar-show',
-  TOUCH_CONTROLLER: 'controller'
-};
-
-
-/**
- * Sprite definition layout of the spritesheet.
- * @enum {Object}
- */
-Runner.spriteDefinition = {
-  LDPI: {
-    CACTUS_LARGE: {x: 332, y: 2},
-    CACTUS_SMALL: {x: 228, y: 2},
-    CLOUD: {x: 86, y: 2},
-    HORIZON: {x: 2, y: 54},
-    PTERODACTYL: {x: 134, y: 2},
-    RESTART: {x: 2, y: 2},
-    TEXT_SPRITE: {x: 484, y: 2},
-    TREX: {x: 677, y: 2}
-  },
-  HDPI: {
-    CACTUS_LARGE: {x: 652,y: 2},
-    CACTUS_SMALL: {x: 446,y: 2},
-    CLOUD: {x: 166,y: 2},
-    HORIZON: {x: 2,y: 104},
-    PTERODACTYL: {x: 260,y: 2},
-    RESTART: {x: 2,y: 2},
-    TEXT_SPRITE: {x: 954,y: 2},
-    TREX: {x: 1338,y: 2}
-  }
-};
-
-
-/**
- * Sound FX. Reference to the ID of the audio tag on interstitial page.
- * @enum {string}
- */
-Runner.sounds = {
-  BUTTON_PRESS: 'offline-sound-press',
-  HIT: 'offline-sound-hit',
-  SCORE: 'offline-sound-reached'
-};
-
-
-/**
- * Key code mapping.
- * @enum {Object}
- */
-Runner.keycodes = {
-  JUMP: {'38': 1, '32': 1},  // Up, spacebar
-  DUCK: {'40': 1},  // Down
-  RESTART: {'13': 1}  // Enter
-};
-
-
-/**
- * Runner event names.
- * @enum {string}
- */
-Runner.events = {
-  ANIM_END: 'webkitAnimationEnd',
-  CLICK: 'click',
-  KEYDOWN: 'keydown',
-  KEYUP: 'keyup',
-  MOUSEDOWN: 'mousedown',
-  MOUSEUP: 'mouseup',
-  RESIZE: 'resize',
-  TOUCHEND: 'touchend',
-  TOUCHSTART: 'touchstart',
-  VISIBILITY: 'visibilitychange',
-  BLUR: 'blur',
-  FOCUS: 'focus',
-  LOAD: 'load',
-  GAMEPADCONNECTED: 'gamepadconnected'
-};
-
-
-Runner.prototype = {
-  /**
-   * Whether the easter egg has been disabled. CrOS enterprise enrolled devices.
-   * @return {boolean}
-   */
-  isDisabled: function() {
-    return loadTimeData && loadTimeData.valueExists('disabledEasterEgg');
-  },
-
-  /**
-   * For disabled instances, set up a snackbar with the disabled message.
-   */
-  setupDisabledRunner: function() {
-    this.containerEl = document.createElement('div');
-    this.containerEl.className = Runner.classes.SNACKBAR;
-    this.containerEl.textContent = loadTimeData.getValue('disabledEasterEgg');
-    this.outerContainerEl.appendChild(this.containerEl);
-
-    // Show notification when the activation key is pressed.
-    document.addEventListener(Runner.events.KEYDOWN, function(e) {
-      if (Runner.keycodes.JUMP[e.keyCode]) {
-        this.containerEl.classList.add(Runner.classes.SNACKBAR_SHOW);
-        document.querySelector('.icon').classList.add('icon-disabled');
-      }
-    }.bind(this));
-  },
-
-  /**