Wave

x = 0
y = 1
while true do
  for i = 1, 20 do
    x = x + 1
    if x == 20 then
      x = 2
    end
    y = x
    if x > 10 then
      y = 20 - x
    end
    for j = 1, y do
      if j ~= y then
        write("#")
      else
        write(">")
      end
    end
    if i ~= 20 then
      print(" ")
    end
  end
  os.sleep(0.15)
  term.clear()
  term.setCursorPos(1,1)
end