L-Systems are described very well on Paul Bourke's website.

The following is the list of available sections:

• axiom: initial state of the system
• rules: list of rewrite rules that are applied on each iteration
• depth: how deep we are allowed to go recursively
• angle: if specified, this argument governs rotation angle. Can be overridden with actions
• actions: list of graphic commands that are triggered by a matching character in the evolved system. The following is the list of available actions:
  • draw(x) draw x units in current direction
  • move(x) move x units in current direction without drawing
  • rotate(deg) rotate current direction deg degrees around Z axis
  • rotateX(deg) rotate current direction deg degrees around X axis
  • rotateY(deg) rotate current direction deg degrees around Y axis
  • push() saves current render state onto stack
  • pop() restores previously saved render state
  • setColor(color) set the current color value, '#ffa500' or 'orange'.
  • swapAngle() swaps the meaning of `+` and `-`.

  By default the following actions are added automatically:

  actions:
    F => draw(10)
    f => move(10)
    + => rotate(60)
    - => rotate(-60)
    & => swapAngle()
    [ => push()
    ] => pop()
  

• width: width in pixels of the drawn line
• color: color of the line. Accepts names and hex. E.g. blue, works the same as #0000ff
• stepsPerFrame: how many steps we are allowed to render per single frame. If set to -1 the scene is rendered immediately. This could be dangerous on deep systems, as the entire system traversal may exhaust the browser's resources.
• direction: three numbers separated by coma x, y, z that set initial direction
• position: three numbers separated by coma x, y, z that set initial position