computercraft fireworks screensaver animation

fireworks.lua

-- Fireworks screensaver animation
-- By L0laapk3, based on Rectar's Fireworks

launchRate = 0.03

fireworks = {}
particles = {}
fcolors={1,2,4,8,16,32,64,512,1024,2048,8192,16384}
particleChars = {"#","X","+","*","."}

starsChance = "+x*..."
stars = {}

function getWidth()
	local w, h = term.getSize()
	return w
end
function getHeight()
	local w, h = term.getSize()
	return h
end

-- function generateStars()
local w, h = term.getSize()
local QSIZE = 7
for xQ = 1, w + QSIZE, QSIZE do
    for yQ = 1, h + QSIZE, QSIZE do
        local star = {}
        star.x = xQ + 1 + math.floor(math.random() * QSIZE)
        star.y = yQ + 1 + math.floor(math.random() * QSIZE)
        local charI = math.floor(#starsChance * math.random())
        star.char = starsChance:sub(charI, charI)
        local closeColors = charI <= math.random() * #starsChance
        star.color1 = closeColors and 0x1 or 0x80
        star.color2 = closeColors and 0x80 or 0x100
        star.blinkI = math.random()
        star.blinkIncr = .02 * math.random()
        star.blinkDecr = .15 * math.random()
        star.isBright = math.random() > .2
                    
        stars[#stars + 1] = star
    end
end

function drawStars()
    for i = 1, #stars do
        local star = stars[i]
        term.setCursorPos(star.x, star.y)
        if star.isBright then
            term.setTextColor(star.color1)
            star.blinkI = star.blinkI - star.blinkDecr
            if star.blinkI <= 0 then
                star.isBright = false
            end
        else
            term.setTextColor(star.color2)
            star.blinkI = star.blinkI + star.blinkIncr
            if star.blinkI >= 1 then
                star.isBright = true
            end
        end
        term.write(star.char)
    end
end

function launchFirework()
	local firework = {}
	firework.x = (1.2 * math.random() - 0.1) * getWidth()
	firework.y = getHeight()
	firework.vx = (math.random()-0.5) * .7
	firework.vy = -((math.random())+3)
	--firework.vy = (-math.random())*2
 firework.color = colors.white

	table.insert(fireworks, firework)
end

function drawFireworks()
	for k,firework in pairs(fireworks) do
		local dx = math.floor(firework.x)
		local dy = math.floor(firework.y)
		term.setCursorPos(dx,dy)
		term.setTextColor(firework.color)	
    term.write(-firework.vx * 1.5 > -firework.vy and "\\" or firework.vx * 1.5 > -firework.vy and "/" or "|")
	end
end

function spawnParticles(x, y)
    local particleColor = fcolors[math.floor(math.random()*#fcolors)+1]
    local numPart = math.floor(math.random() * 90) + 20
    local commonPartSpeed = .25 + .45 * math.random()
    for i=1,numPart do
        local particle = {}
        particle.x = x
        particle.y = y
        particle.c = particleColor
        local angle = i * 6.283185 / numPart
        local z = math.random()
        particle.vx = math.sin(angle) * 3 * z * commonPartSpeed
        particle.vy = math.cos(angle) * 2 * z * commonPartSpeed
        particle.life = 1
        particle.lifeSpeed = .2 + .8 * math.random()
        table.insert(particles, particle)
    end	
end

function updateFireworks()
	local toRemove = {}
	for k,firework in pairs(fireworks) do
		firework.x = firework.x + firework.vx
		firework.y = firework.y + firework.vy
		
		firework.vx = firework.vx * 1.1
		firework.vy = firework.vy * 0.9
		if firework.vy > -0.5 then
            spawnParticles(firework.x, firework.y)
			table.insert(toRemove, k)
		end
	end
	for k,v in pairs(toRemove) do
		table.remove(fireworks, v)
	end
end

function drawParticles()
 term.setBackgroundColor(colors.black)
	for k,particle in pairs(particles) do
		local dx = math.floor(particle.x)
		local dy = math.floor(particle.y)
		local pchar = particleChars[math.floor(particle.life)] or ""
		term.setTextColor(particle.c)
		term.setCursorPos(dx, dy)
		term.write(pchar)
	end
end
function updateParticles()
	local toRemove = {}
	for k,particle in pairs(particles) do
		particle.x = particle.x + particle.vx
		particle.y = particle.y + particle.vy
		
		particle.vx  = particle.vx * .98
		particle.vy = particle.vy * .98 + 0.01
		
		particle.life = particle.life + particle.lifeSpeed * math.random()
		if particle.life >= 6 then
			table.insert(toRemove,k)
		end
	end
	for k,v in pairs(toRemove) do
		table.remove(particles,v)
	end
end



local window = window.create(term.current(), 1, 1, w, h)
term.redirect(window)
launchFirework()

local tid = os.startTimer(.05)
while true do
    local e, etid, x, y = os.pullEvent()
    if e == "timer" and tid == etid then
        tid = os.startTimer(.05)
        if math.random() > 1 - launchRate then
            launchFirework()
        end
        updateFireworks()
        updateParticles()
        window.setVisible(false)
        term.clear()
        drawStars()
        drawFireworks()
        drawParticles()
        window.setVisible(true)
    elseif e == "mouse_click" then
        spawnParticles(x, y)
    end
end

works best on medium-large size monitors, monitor scale <dir> 0.5 can also help.