tic80-stuff/particles.lua

-- title:  simple particle system
-- author: pixelbath
-- desc:   basic particle system, first used in Alter Ego by Kyuchumimo
-- script: lua

t=0
x=96
y=24

particles = {}
particletype = 'stars'
local starcolors = { 1, 2, 13, 15}
-- numparticles = number of particles to show
-- particletype = rain|snow|stars
function particleinit(numparticles, type)
	-- initialize
	particles = {}
	particletype = type
	for i = 0, numparticles do
		table.insert(particles, {
			x = math.random() * 240,
			y = math.random() * 136,
			lastx = 0,
			lasty = 0,
			color = 2,
			t = 0,
			vel = 0,
		})
	end
	if particletype == 'stars' then
		for i = 1, #particles do
			particles[i].twinkle = math.random() > 0.49 -- randomly pick true/false
			particles[i].color = starcolors[math.random(#starcolors)]
		end
	end
	if particletype == 'rain' then
		for i = 1, #particles do
			particles[i].vel = math.random(3) + 1
			if particles[i].vel > 2.5 then
				particles[i].color = 8
			end
		end
	end
	if particletype == 'snow' then
		for i = 1, #particles do
			particles[i].color = 15
			particles[i].vel = math.random() + 0.2
		end
	end
end

function particleupdate()
	if particletype == 'stars' then
		for i = 1,#particles do
			local p = particles[i]
			if not p.twinkle then goto continueTwinkle end
			::continueTwinkle::
			if t % 15 == 0 and math.random() > 0.1 then
				p.color = starcolors[math.random(#starcolors)]
			end
		end
	end
	if particletype == 'rain' then
		for i = 1,#particles do
			local p = particles[i]
			if p.lasty and p.lasty > 136 then
				p.y = 0
				p.lasty = 0
				p.x = math.random() * 240
			end
			p.lasty = p.y
			p.lastx = p.x
			p.x = p.x - p.vel / 5
			p.y = p.y + p.vel * 1.5
		end
	end
	if particletype == 'snow' then
		for i = 1,#particles do
			local p = particles[i]
			if p.y and p.y > 136 then
				p.y = 0
				p.lasty = 0
				p.x = math.random() * 240
			end
			p.x = p.x - (math.random() - 0.4)
			p.y = p.y + p.vel
		end
	end
end

function particledraw()
	if (particletype == 'rain') then
		for i = 1,#particles do
			local p = particles[i]
			line(p.x, p.y, p.lastx, p.lasty, p.color)
		end
		return
	end
	for i = 1,#particles do
		local p = particles[i]
		pix(p.x, p.y, p.color)
	end
end

-- init here for title screen
particleinit(150, 'snow')


function TIC()

	if btn(0) then y=y-1 end
	if btn(1) then y=y+1 end
	if btn(2) then x=x-1 end
	if btn(3) then x=x+1 end

	cls(13)
	spr(1+t%60//30*2,x,y,14,3,0,0,2,2)
	print("HELLO WORLD!",84,84)

	particleupdate()
	particledraw()
	
	t=t+1
end

-- <TILES>
-- 001:eccccccccc888888caaaaaaaca888888cacccccccacc0ccccacc0ccccacc0ccc
-- 002:ccccceee8888cceeaaaa0cee888a0ceeccca0ccc0cca0c0c0cca0c0c0cca0c0c
-- 003:eccccccccc888888caaaaaaaca888888cacccccccacccccccacc0ccccacc0ccc
-- 004:ccccceee8888cceeaaaa0cee888a0ceeccca0cccccca0c0c0cca0c0c0cca0c0c
-- 017:cacccccccaaaaaaacaaacaaacaaaaccccaaaaaaac8888888cc000cccecccccec
-- 018:ccca00ccaaaa0ccecaaa0ceeaaaa0ceeaaaa0cee8888ccee000cceeecccceeee
-- 019:cacccccccaaaaaaacaaacaaacaaaaccccaaaaaaac8888888cc000cccecccccec
-- 020:ccca00ccaaaa0ccecaaa0ceeaaaa0ceeaaaa0cee8888ccee000cceeecccceeee
-- </TILES>

-- <WAVES>
-- 000:00000000ffffffff00000000ffffffff
-- 001:0123456789abcdeffedcba9876543210
-- 002:0123456789abcdef0123456789abcdef
-- </WAVES>

-- <SFX>
-- 000:000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000304000000000
-- </SFX>

-- <PALETTE>
-- 000:1a1c2c5d275db13e53ef7d57ffcd75a7f07038b76425717929366f3b5dc941a6f673eff7f4f4f494b0c2566c86333c57
-- </PALETTE>