# L-Systems: Quick Rules (For kidz only)

Yo dude,
Like, here is the quick and dirty for learning how to create your own fractals:

Start by choosing the Fern preset.
Click next button twice to draw second generation of the fern shown below.

In the figure above, the angle of the red branch with the green stem is made by the 5+.
This makes 5 right turns of 8° each (that's 40° total - I'm smart. I can multiply).
The f symbol is what actually draws the red branch.

Change the Turn Angle from 8 degrees to 12 degrees.
Then click clear and click next twice to draw second generation.
This makes each + symbol a 12 degree turn.
Notice that all the branches are wider.

Alright. This time, change the Turn Angle to 3 degrees.
Click the clear button again, and click next twice.
This creates the skinny fern below:
.

Now, it is time to mess with that Axiom thing.
The Axiom is the start - the beginning - the initial string: generation zero.
OK.
Hit that clear button again.
The display shows one straight line segment.
That is the axiom.
The axiom is 'f'.
A single 'f' is a single line segment.
.
Amazing!

Now, change the axiom from the single 'f' to three of them 'f' things: 'fff'
Hit clear and you have three line segments: red, green and blue.
.

If the Turn Angle is not set to 3 degrees, then set it to 3 degrees and hit clear.

Now, hit next two or three times, and behold the result.
The thing now looks more like a grass then a fern.
Can you explain what happened?

Alright. Lets move no the rule area.
Click the reset button to restore the original fern preset.
Notice that there is one rule in the rule field.
The rule is: f=|[5+f][7-f]-|[4+f][6-f]-|[3+f][5-f]-|f
Try changing some of the numbers.
Make one of the fives a two or the three an eight.
Click clear and next.

Can you figure out what happened?

You can add lots of letters like q, r, s, and t to the rules, but most of them will not do anything.
Only the 'f', 'h' and '|' symbols cause a line to be drawn.
The '+' and '-' symbols cause the next line to be drawn in a different direction.
There are a few other command symbols summarized in the table below.

 f, h Draw while moving one step forward. g Move one step forward without drawing. | Draw while moving forward. The length of the line depends on the symbol's age. + Turn right. - Turn left. [ This save the draw location and the draw direction. . ] This restores the draw location and the draw direction that was last saved. For example, f+[++++f]f The first f draws a line up. Then the + makes a right turn. Next, the [ saves this location and direction. Inside the brackets there is 4 right turns and another line drawn. However, the closing bracket, ] moves the drawing pen back to where it was after drwing the first f+. Thus, the final f is drawn from where the pen was before the [. 0-9 Repeat (i.e. '+++' is the same as '3+').

Now - start creating!
Oh - the things you can do...
And like, Ya.

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