#Draw Tribe

#Purpose

The Draw tribe section controls what pointer input writes into the grid. Drawing is live editor input:
it sends brush commands to the WebGPU worker, which mutates the active grid buffer and updates the render preview.

#Controls

• Tribe swatches:
  One swatch is shown for each non-dead tribe. Clicking a swatch toggles it in the draw selection. Multiple selected tribes are used as random brush candidates.
• Delete swatch:
  Toggles delete mode. Delete mode simply writes the dead tribe.
• Size:
  Brush size in cells. The value is clamped between $1$ and $\frac{1}{4}$ of the smaller grid dimension. The UI shows Min 1 or Max N when input is invalid or capped.
  This field is persisted across sessions.
• Shape:
  Brush footprint. Available values are square, round, diamond, vertical line, and horizontal line.
  This field is persisted across sessions.
• Mode:
  Brush fill behavior. Full targets every cell in the footprint, Spray treats the footprint as a randomized spray area, and Outline targets only the border of the chosen shape.
  This field is persisted across sessions.
• Density:
  Brush density percentage for the current mode. The value is clamped from $1$ to $100$. Each mode stores its own density, so switching between Full, Spray, and Outline restores that mode's last value. Defaults are $100\%$ for Full and Outline, and $50\%$ for Spray.
  In Full and Outline mode, cells in the footprint that are not selected by density stay unchanged. In Spray mode, cells in the footprint that are not selected by density become dead.
  This field is persisted across sessions.
• Touch:
  Mobile-only control. Draw makes touch input paint cells, while Pan makes touch input move the camera. Two-finger touch always performs pinch zoom.

#Canvas Behavior

Left mouse or primary pointer input draws. Right mouse input pans. Mouse wheel zooms around the pointer. Touch input draws or pans depending on the Touch control, and $2$ active touch pointers switch to pinch zoom.

Brush edge behavior follows the grid topology from Grid size. In toroidal mode, brushes wrap across grid edges. Internally, a wrapped brush stroke is split into up to $4$ non-wrapping dispatch rectangles so the shader can update packed cells without special cross-edge writes inside $1$ dispatch. In bounded mode, brushes clip at the grid edge and do not paint the opposite side.