Every uppercase letter (A–Z) draws forward. Every lowercase letter (a–z) moves forward without drawing. + turns left; - turns right. [ saves the pen’s position and direction; ] restores them. Every letter can also have a replacement rule. Direction 0° points right; 90° points up.
A–Z
a–z
+
-
[
]
Generation 0 is the starting string. Each generation applies all the rules once. The drawing always fits the frame.
Enable JavaScript to generate fractals and explore their rules.