forward(300)left(90)forward(300)right(90)pen(1)

repeat(15) {
  repeat(15) {
    repeat(4) {
      forward(30)
      right(90)
    }
    pen(0)
    right(90)
    forward(40)
    left(90)
    pen(1)
  }
  pen(0)
  forward(-40)
  left(90)
  forward(600)
  right(90)
  pen(1)
}