paper 100
pen 20
command box L R T B
{
   repeat A L R
   {
      line A T A B}
   }

   box 40 80 80 40
   box 20 60 60 20

   repeat a 20 21
   {
      repeat b 39 40
      {
         line 60 a 80 b
      }
   }

   repeat a 20 21
   {
      repeat b 39 40
      {
         line a 60 b 80
      }
   }
   pen 100
   repeat a 20 21
   {
      repeat b 39 40
      {
         line a 20 b 40
      }
   }

   repeat a 60 61
   {
      repeat b 79 80
      {
         line 60 a 80 b
      }
   }