Fun with L-systems

I haven't done much with javascript embedded in HTML before, but I had some fun today before and after our graduation ceremony (congratulations, Clifton, Dan and Karl!). For information about L-systems, see Wikipedia. Edit the following to your satisfaction. Feel free to view the source of this post, and I hereby release this post and its source code into the public domain.
If you click on "Go" with the default settings, you'll get a Koch snowflake. Here are some other systems to explore:

• Pythagoras tree
• Dragon curve
• Space fill (rules from here)
• Sierpinski's triangle
• plant (from Wikipedia)

Axiom:
Rules:

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Actions:

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Preamble:
Iterations:
Show transformed text: