To corner :SIZE
Rt 45
Fd :SIZE
Rt 45
End

To one_side :SIZE :DIAG :LEVEL
If :LEVEL = 0 [STOP]
ONE_SIDE :SIZE :DIAG :LEVEL - 1
Rt 45 Fd :DIAG Rt 45
ONE_SIDE :SIZE :DIAG :LEVEL - 1
Lt 90 Fd :SIZE Lt 90
ONE_SIDE :SIZE :DIAG :LEVEL - 1
Rt 45 Fd :DIAG Rt 45
ONE_SIDE :SIZE :DIAG :LEVEL - 1
End

To sierp :SIZE :LEVEL
Make "DIAG :SIZE / SQRT 2
Repeat 4 [ONE_SIDE :SIZE :DIAG :LEVEL CORNER :DIAG]
End

