Dragon Curves

Dragon Curves where discovered by three physicists at NASA (John E. Heighway, Bruce A. Banks, and William G. Harter) and first published by Martin Gardner in Scientific American (March and April 1967).

If the edges are replaced by slightly rounded curves, we get curves that do not cross each other.

Replacement Rules:

Initial text: "FX"

"X" -> "X+YF+"

"Y" -> "-FX-Y"

Drawing instructions:

Grade 1 "F+F+"

Grade 2 "F+F++-F-F+"

Grade 3 "F+F++-F-F++-F+F+--F-F+"