L-System Generator

Edit rewrite rules, draw turtle graphics and inspect the expanded word.

Your data stays on this deviceGenerated locally, without an account or upload.

UTF-8 TXT or exported settings JSON; at most 1 MiB.

Choose settings, then generate.

Understand the concept

An L-system replaces symbols simultaneously in each generation. An axiom starts the process. Drawing is a separate interpretation: F may draw, f may move, + and − turn, and [ / ] save and restore the turtle position.

What you can do

Enter deterministic single-character rules, separate drawing and movement symbols, and inspect or download the full expanded word. The drawing uses the same word and can be exported as vector or raster.

How to use

Enter an axiom and one rule per line, for example F=F+F--F+F. Set draw symbols to F.
Choose 60° and three iterations for a Koch edge. Generate, inspect the word and correct any bracket or rule error.
Inspect the result and numeric report. Download SVG for editable vectors, PNG for a fixed image, or JSON to restore these settings later.

Limits and common errors

Only deterministic context-free rules are accepted; no user JavaScript, stochastic or parametric syntax. Rules use ASCII letters/digits. Growth is checked before expansion; the symbol and primitive limits still apply.

Frequently asked questions

Why is there a word but no line?

Rewriting and drawing are separate. If the word contains only A and B while the draw field contains F, the word is valid but no segment is drawn. Add the intended drawing symbols, or use the TXT export for a symbolic sequence.

Your data stays on this device?

Generated locally, without an account or upload.