#!/usr/bin/env yabasic
w = 512
open window w, w
sleep 1
backcolour 0,0,0
clear window
for i=0 to w step 10
  v = 255 * i / w
  color 0, v, (255 - v)
  line 0, i, i, w
  color (255 - v), 0, v
  line i, 0, w, i
  pause 0.025
next i
sleep 3
end