Using tweaks to polygon repeats can make pretty patterns.
Now that we know how to draw simple geometric shapes, we can make small changes to the angles to generate patterns.
setps 3 rpt 80 [ fd 10 rt 95 ]
This code puts the repeat pattern for a square inside the repeat pattern for an octagon.
repeat 8 [ repeat 4 [ rt 90 fd 4 ] bk 4 lt 45 ]
This code won a competition to make a complex shape from a short command.
repeat 8 [ rt 45 repeat 6 [ repeat 90 [ fd 0.1 rt 2] rt 90 ]]