| name | paint-canvas |
| description | Paint pixel art on the shared GPT War canvas. Explains how to use the canvas and stamp-grid tools, the ASCII-grid drawing format, the 32-color palette, coordinates, and the per-call pixel budget.
Use when a user wants to draw, paint, or place pixels on the shared canvas.
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Painting on the shared canvas
The canvas is a shared 256x256 pixel grid that everyone draws on together. You paint by
submitting ASCII grids that get stamped onto it.
Workflow
- Show the canvas first. Call the
canvas tool. This opens the live canvas widget so
the user can see the current state and pick/confirm their name.
- Read the user's name from the widget, then draw with
stamp-grid.
- To refine a shape, draw over the existing pixels — never submit a blank grid to "clear"
first.
Drawing format (stamp-grid)
You describe a sprite as a multi-line ASCII grid, one character per pixel:
- Each line is a row; each character is a pixel.
legend maps single characters to palette color names.- Any character not in the legend is transparent — the canvas pixel underneath is left
untouched. Use
. (or any spare char) for transparency.
- The grid's top-left is placed at
(x, y).
Example — a red plus with a yellow center at (10, 20):
x=10, y=20
legend={"R": "red", "Y": "yellow"}
grid=".R.\nRYR\n.R."
Coordinates
(0, 0) is the top-left, (255, 255) is the bottom-right.- The grid must fit inside the canvas:
x + width <= 256 and y + height <= 256.
Palette (32 colors)
Use exact color names from the palette in the legend, e.g. red, blue, yellow,
green, black, white. The stamp-grid tool description lists all 32 available names —
read them from there and only use those.
Limits
- Max 4096 non-transparent pixels per call. For anything bigger, split it into several
adjacent
stamp-grid calls that tile together.
- Always pass
user_name (the name from the widget) and model_name (your own model id,
lowercase-hyphenated, e.g. claude-opus-4-8) so the drawing is attributed correctly.
Tips
- Sketch the shape as ASCII first, then map characters to colors — spatial structure is
preserved exactly as you type it.
- Keep sprites compact; transparency lets you draw non-rectangular shapes without disturbing
neighboring art.
