hurp.lua

local component = require("component")
local os = require("os")
local gpu = component.gpu
local w,h = gpu.getResolution()
local tick = 1/(h/2)
local white = true
local black = true
local whiteCol = 16777215
local blackCol = 0

function setup()
  gpu.setBackground(0x000000)
  gpu.setForeground(0xFFFFFF)
  gpu.fill(1,1,w,h," ")
end

function fromWhite()
  if white then
    whiteCol = whiteCol-1
  else
    whiteCol = whiteCol+1
  end
  if whiteCol == 0 then
    white = false
  elseif whiteCol == 16777215 then
    white = true
  end
  --print(whiteCol)
  return whiteCol
end

function fromBlack()
  if black then
    blackCol = blackCol+1
  else
    blackCol = blackCol-1
  end
  if blackCol == 16777215 then
    black = false
  elseif blackCol == 0 then
    black = true
  end
  --print(blackCol)
  return blackCol
end

function aniIn()
  for i=1, h/2 do
    setup()
    gpu.setBackground(fromWhite())
    gpu.fill(i,i,w-(i*2)+2,h-(i*2)+2," ")-- this line
    gpu.setBackground(fromBlack())
    gpu.fill(i+1,i+1,w-(i*2),h-(i*2)," ")
    os.sleep(tick)
  end
end

function aniOut()
  for i=h/2, 1, -1 do
    setup()
    gpu.setBackground(fromWhite())
    gpu.fill(i,i,w-(i*2)+2,h-(i*2)+2," ")
    gpu.setBackground(fromBlack())
    gpu.fill(i+1,i+1,w-(i*2),h-(i*2)," ")
    os.sleep(tick)
  end
end

function main()
  aniIn()
  aniOut()
end

while true do
  main()
end