Axiom: A
context().turtle.setAngleIncrement(90)

derivation length: 2
production:

A --> B-F+CFC+F-D&F^D-F+&&CFC+F+B//
B --> A&F^CFB^F^D^^-F-D^|F^B|FC^FA//
C --> |D^|F^B-F+C^F^A&&FA&F^C+F+B^F^D//
D --> |CFB-F+B|FA&FA&&FB-F+B|FC//

interpretation:


endlsystem
