startshape LIMIT

rule LIMIT {

4*{r 90 h 90} QUAD [r 45 x .5 y .5 h 45 sat 1 b 1 |b 0]

}

rule SHAPE {

SQUARE{a -.5}
CIRCLE{s .8 sat -1 b 1 a -.5 z 1}

}

rule QUAD {

SHAPE{}
2*{x -1 y 1} QUAD [x .5 y -.5 s .618 x .5 y .5 b .15| h 90]

}