paper 100
antialias 1

command griddify_normal
{
   pen (100 -<time 4>)
   repeat n 0 9
   {
      line 0 50 50 (5+10*n)
      line 50 (5+10*n) 100 50
      line 50 0 50 100
   }
}

command griddify_time
{
   pen <time 4>
   repeat n 0 9
   {
      line 50 0 (5+n*10) 50
      line (5+n*10) 50 50 100
   }
}

forever
{
   griddify_normal
   griddify_time
}