per

maxChange = 2

mon = peripheral.wrap("right")

x, y = mon.getSize()
ceny = y / 2

height = ceny



function draw(coll)
  mon.setCursorPos(coll, height)
  for i = height, y do
    mon.setCursorPos(coll, i)
    mon.write(" ")
  end
  sleep()
end

function perlin()
  step = 0
  repeat
    rand = math.random()
    sleep()
    if rand > 0.8 then
      randup = math.random(maxChange)
      --if randup < 1.9999 then
        up = 1
      --else
        --up = 2
      --end
      height = height + up
      draw(step)
    elseif rand < 0.2 then
      randdown = math.random(maxChange)
      --if randdown < 1.9999 then
        down = 1
      --else
      --  down = 2
      --end
      height = height - down
      draw(step)
    else
      draw(step)
    end
    step = step + 1
  until step == legnth
end

while true do
  legnth = x
  height = ceny
  perlin()
  mon.setBackgroundColor(colors.black)
  mon.clear()
  mon.setBackgroundColor(colors.white)
  sleep(1)
end