paint-canvas

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.

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

1. 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.
2. Read the user's name from the widget, then draw with stamp-grid.
3. 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.