Parses axioms and rules and runs a simulation with the given
parameters. Use the Preset selector in the bottom for
some pre-filled shapes.
Axiom: initial statement to start the expansion from.
Rules: sequence of newline-separated replacement rules.
Initial angle: starting direction the drawing pen is pointing in, in
degrees. This simulation uses canvas coordinates (y grows downward);
to start pointing up, the initial angle should be set at 180.
Angle change: degrees for each turn command.
Scale multiplier: length multiplier for each recursive step.
Simulation depth: how many recursion steps to perform.