---
title: Chess
description: Drag-to-move chess on the Finder desktop, a denser example of positioning, drag input, and host round-trips.
---

Chess puts more load on the renderer than [Pong](/docs/examples/pong). The renderer,
host bridge, and native layer have to agree on position, drag interaction, and
timing while a full board is on screen. The source is in the Finder Mode
repository under
[`games/chess`](https://github.com/methodacting/finder-mode/tree/main/games/chess).

## Modes

- Solo: play the built-in AI (js-chess-engine). The AI waits 1.2 seconds before
  replying so its move reads as a reply.
- Multiplayer: two machines share a board through a game-server Durable Object.
  Both sides join a room code.

From the Finder Mode repository root:

```bash
pnpm chess                  # solo vs computer
pnpm chess:multi create     # host a room
pnpm chess:multi join <room>
```

Like Pong, chess calls `startSession` with the default options, so your existing
Desktop items are hidden in place for the game and shown again when it quits.

## How it maps onto Finder

- The board is a [Wallpaper](/docs/reference/components/wallpaper) image. Each piece
  is a pooled [Sprite](/docs/reference/components/sprite) with a library-minted
  invisible name, placed on a square computed from the board's origin and cell
  size.
- You drag a piece and the game reads where you dropped it, rounds that to the
  nearest square, and asks the engine to make the move. An illegal move, a move
  out of turn, or (in multiplayer) a server rejection leaves the piece's
  position unchanged, and the Stage moves the file back.
- Captured pieces line up in a tray for each colour. The turn indicator, the
  check banner, and the tray headers are pre-baked sprites in their own Stage,
  shown by moving them out of the park.
- The game-over text uses `<Text onDemand />`, so its files are created fresh
  and draw above any piece the player dragged. `R` restarts the game.

Because it relies on absolute positioning and host round-trips, read chess
alongside the [Architecture](/docs/reference/architecture) and
[Host Runtime](/docs/reference/host-runtime) pages rather than as a first
introduction.