Invaders generator for LÖVE

invaders_generator.lua

local lg = love.graphics
local rnd = math.random

local canvas
local show_help
local invader_sz
local invader_num

local function hsv2rgb(H, S, V)   -- 0...360
    local Hi = math.floor(H / 60) % 6
    S = S or 75 -- saturate
    V = V or 75 -- brightness
    local Vmin = ((100 - S) * V) / 100
    local a = (V - Vmin) * ((H % 60) / 60)
    local Vinc = Vmin + a
    local Vdec = V - a
    local r, g, b
    if     Hi == 0 then r = V; g = Vinc; b = Vmin
    elseif Hi == 1 then r = Vdec; g = V; b = Vmin
    elseif Hi == 2 then r = Vmin; g = V; b = Vinc
    elseif Hi == 3 then r = Vmin; g = Vdec; b = V
    elseif Hi == 4 then r = Vinc; g = Vmin; b = V
    elseif Hi == 5 then r = V; g = Vmin; b = Vdec
    else assert(false)
    end
    return {r/100, g/100, b/100}
end

local function create_invader(x0, y0, w, size)
    local rndColor = {}

    local h = rnd(359)
    local s = rnd(50, 100)
    local v = rnd(50, 100)
    rndColor = {
        hsv2rgb(h     , s, v),
        hsv2rgb(h + 40, s, v),
        hsv2rgb(h + 80, s, v),
        {0, 0, 0},
        {0, 0, 0},
        {0, 0, 0}
    }
    rndColor[0] = #rndColor
    local middle = math.floor(size / 2)

    for y = 0, size-1 do
        local color = {}
        for x = 0, size-1 do
            local c
            if x < middle then
                c = rndColor[rnd(rndColor[0])]
                table.insert(color, c)
            elseif x == middle then
                c = rndColor[rnd(rndColor[0])]
            else
                c = table.remove(color)
            end

            local X = x * w + x0
            local Y = y * w + y0
            lg.setColor(c)
            lg.rectangle("fill", X, Y, w, w)
        end
    end
end

local function generate()
    local sx, sy = lg.getDimensions()
    canvas = lg.newCanvas(sx, sy)

    local invaderW = sx / invader_num
    local padding = invaderW / (invader_sz)

    lg.setCanvas(canvas)
    for x = 0, invader_num-1 do
        for y = 0, invader_num-1 do
            local X = x * invaderW + padding
            local Y = y * invaderW + padding
            local W = (invaderW - padding * 2) / invader_sz
            create_invader(X, Y, W, invader_sz)
        end
    end
    lg.setCanvas()
end

function love.load(arg)
    math.randomseed(os.time() + tonumber(tostring({}):sub(8)))
    invader_sz = arg[1] or 7
    invader_num = arg[2] or 8
    generate()
    
    show_help = true
    local font = love.graphics.newFont(16)
    love.graphics.setFont(font)
end

function love.draw()
    --// canvas start
    lg.setColor(1, 1, 1, 1)
    lg.draw(canvas)
    --\\ canvas end
    
    if show_help then
        lg.setColor(1, 1, 1, 1)
        lg.print([[
Esc     quit
Space   reload
Num+ +  larger invaders
Num- -  smaller invaders
Num* ]  more invaders
Num/ [  less invaders
F1      show/hide help
]])
    end
end

function love.keyreleased(k, s, r)
    if k == "escape" then
        love.event.quit()
    elseif k == "space" then
        generate()
    elseif k == "kp+" or s == "=" then
        invader_sz = invader_sz + 2
        generate()
    elseif k == "kp-" or s == "-" then
        invader_sz = math.max(3, invader_sz - 2)
        generate()
    elseif k == "kp*" or s == "]" then
        invader_num = invader_num + 1
        generate()
    elseif k == "kp/" or s == "[" then
        invader_num = math.max(1, invader_num - 1)
        generate()
    elseif k == "f1" then
        show_help = not show_help
    end
end