//exercise 3A
Command square  l r
{
   line l l r l
   line l l l r
   line r l r r
   line l r r r
}
Command diamond a b half
{
   line half a b half
   line half a a half
   line a half half b
   line b half half b
}
Command pattern3A y
{
   repeat m 0 10
   {
      pen (m*y)
      set n (m*m*m)
      set x n
      square x y

  square (x+(y/4)) (y-(y/4))
  square ((x+(y/4))+((y/2)-(y/4/2))) 
       ((y-(y/4))-((y/2)-(y/4/2)))
 }
}
//exercise 3B
Command pattern3B A
{
   forever
   {
      repeat  x 0 50
      {
         set y (x*A)
         set z (x/y)
         //paper x
         pen (100-x)

         line z y (50-z) (50-y)
         line (50-y) z y (50-z)
         line (50-z) (50-y) z y
         line y (50-z) (50-y) z
      }
   }
}

// exercise 3C
Command pattern3C incX
{
   repeat B 0 100
   {
      set A (B*incX)
      pen A
      line A 0 100 A
      line A 100 0 A
      line 0 A (20-A) 0
      pen (100-A)
      line 100 (100-A) 
               (100-(60-A)) 100
   }
}
repeat x 0 100
{
paper x
pattern3C 5
pattern3A 50
pattern3B 20
}