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.
• The RUN button preserves your current zoom and offset. To re-render lines sharply after zooming, simply click RUN again.