turtlefreeze is an interpreter for the esoteric language Brainfuck extended with turtle graphics commands inspired by the Logo language.

Brainfuck Commands

>	increment the data pointer (move right)
<	decrement the data pointer (move left)
+	increment the byte at the data pointer (255 → 0)
-	decrement the byte at the data pointer (0 → 255)
[	if the byte at the data pointer is zero, jump forward to the command after the matching ]
]	if the byte at the data pointer is nonzero, jump back to the command after the matching [

Turtle Commands

N = value of the current memory cell. The cell value remains unchanged.

{	turn turtle left by 360°/N (if N=0 → golden angle ≈137.5°)
}	turn turtle right by 360°/N (if N=0 → golden angle)
^	move turtle forward by N pixels
_	pen down (draw lines when moving)
~	pen up (move without drawing)

Viewport Controls

mouse wheel	zoom relative to cursor position
left click + drag	pan the view
double click	reset view (zoom=1, offset=0)

Tips

• Click any cell on the memory tape to manually input a value (0–255).
• The group +/−/</> checkbox speeds up execution of identical command sequences.

About

Turtlefreeze was created by me uwing several AIs. Its source code is turtlefreeze.tar.bz2. It is licensed as public domain, do whatever you wish.