DVD Logo screensaver (ComputerCraft)

local mon = peripheral.find("monitor")
if mon then
    mon.setTextScale(0.5)
    term.redirect(mon)
end

-- adjusts walls of screen so that it will bounce further/closer to the boundries of the screen
local xMargin, yMargin = 0, 0

local redrawDelay = nil
local changeColors = true

local scr_x, scr_y = term.getSize()
local max, min = math.max, math.min
local floor, ceil = math.floor, math.ceil

if scr_x >= 60 and scr_y >= 25 then
    redrawDelay = redrawDelay or 0.05
else
    redrawDelay = redrawDelay or 0.1
end

local getSize = function(image)
    local x, y = 0, #image[1]
    for y = 1, #image[1] do
        x = max(x, #image[1][y])
    end
    return x, y
end

local drawImage = function(image, x, y, terminal)
    terminal = terminal or term.current()
    local cx, cy = terminal.getCursorPos()
    for iy = 0, #image[1] + 1 do
        terminal.setCursorPos(x - 1, y + (iy - 1))
        if image[1][iy] then
            terminal.blit(
                " " .. image[1][iy] .. " ",
                "f" .. image[2][iy] .. "f",
                "f" .. image[3][iy] .. "f"
            )
        else
            terminal.clearLine()
        end
    end
    terminal.setCursorPos(cx,cy)
end

local colorSwap = function(image, text, back)
    local output = {{},{},{}}
    for y = 1, #image[1] do
        output[1][y] = image[1][y]
        output[2][y] = image[2][y]:gsub(".", text)
        output[3][y] = image[3][y]:gsub(".", back or text)
    end
    return output
end

local logo = {
    xvel = (math.random(0, 1) * 2) - 1,
    yvel = (math.random(0, 1) * 2) - 1,
    x = floor(scr_x / 2),
    y = floor(scr_y / 2),
    img = {
        {
            "  —ƒƒƒƒƒƒƒƒƒ”     Ÿƒƒƒƒƒƒƒ€€",
            "  ‚ƒƒƒ€ˆƒƒ€€    ‡€€‡ƒƒƒƒ‹€‚",
            " —€—€€€€€  ”€• Ÿ€Ÿ€€  •€•",
            " €€€‡€—  ‚€€‡€€‡  —€—  Ÿ€",
            "—€€ƒƒ€€‡    ”€€Ÿ   €‚ƒ€Ÿ ",
            "‚ƒƒƒƒƒ      ‚€‡     ƒƒƒƒƒ   ",
            "      ƒƒƒ‚ƒƒƒ        ",
            " ƒ€€€€€€Ÿ€€€€€€€‚ƒ   ",
            "•€€€€€€ˆ‘€€€€€€€€€Œ€€€€€€€•  ",
            " ƒ€€€€€€‚ƒƒƒƒƒ€€€€€€€Ÿƒ   ",
            "      ƒƒƒƒƒƒƒƒ        ",
        }, {
            "00ffffffffff000000fffffffffff",
            "000000f0f00000000f000000000f0",
            "0f00fff0000f000ff000ff0000f00",
            "0f00fff0000000f00000f0000ff00",
            "f00ff0000000f0000000f0fff0000",
            "00000000000000000000000000000",
            "000000fffffffffffffff00000000",
            "0fff0000000000000000000fff000",
            "f000000f0ffffffffff0000000000",
            "000f000000ffffff0000000000000",
            "00000000000000000000000000000",
        }, {
            "ff0000000000ffffff000000000ff",
            "ffffff000ff00ffff000ffffff00f",
            "f00ffff00ff00ff000fff00fff00f",
            "f00fff00ffff00000fff00fff000f",
            "0000000fffff000fffff000000fff",
            "fffffffffffff0fffffffffffffff",
            "ffffff000000000000000ffffffff",
            "f000000000ffffff0000000000fff",
            "00000000ffffffffff00000000fff",
            "fff00000000000000000000ffffff",
            "fffffffffffffffffffffffffffff",
        }
    }
}

local imgXsize, imgYsize = getSize(logo.img)
local xWall, yWall

local render = function(colorReplace)
    if colorReplace then
        drawImage(
            colorSwap(logo.img, {["0"] = colorReplace}, {["0"] = colorReplace}),
            floor(logo.x),
            floor(logo.y)
        )
    else
        drawImage(
            logo.img,
            floor(logo.x),
            floor(logo.y)
        )
    end
end

local color = math.random(1, 15)

local tick = function()
    scr_x, scr_y = term.getSize()
    xWall = scr_x - imgXsize + 1 - xMargin
    yWall = scr_y - imgYsize + 1 - yMargin
    logo.x = min(max(logo.x + logo.xvel, 1 + xMargin), xWall)
    logo.y = min(max(logo.y + logo.yvel, 1 + yMargin), yWall)

    if floor(logo.x) == (1 + xMargin) or floor(logo.x) == xWall then
        logo.xvel = -logo.xvel
        color = math.random(1, 15)
    end
    if floor(logo.y) == (1 + yMargin) or floor(logo.y) == yWall then
        logo.yvel = -logo.yvel
        color = math.random(1, 15)
    end
    if changeColors then
        render(string.sub("0123456789abcdef", color, color))
    else
        render()
    end
end

term.setBackgroundColor(colors.black)
term.clear()

local evt
local tID = os.startTimer(redrawDelay)
while true do
    evt = {os.pullEventRaw()}
    if evt[1] == "timer" and evt[2] == tID then
        tick()
        tID = os.startTimer(redrawDelay)
    elseif evt[1] == "terminate" then
        render("8")
        sleep(0.05)
        render("7")
        sleep(0.05)
        term.clear()
        break
    end
end

return 0