Local browser sandbox for "duplicate chess" — a four-player coupled-board chess variant invented by Andrew Freiberg. Scaffold per CREATE_PROJECT.md plus the approved design spec from this session's brainstorming. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Duplicate Chess
Local browser sandbox for "duplicate chess" — a four-player coupled-board chess variant.
Start Here
Read the latest handoff first: .claude/handoffs/ (most recent file).
It has session state, in-progress work, and ordered next steps.
Then check IDEA.md for the project brief, DECISIONS.md for settled choices, and
docs/superpowers/specs/2026-05-19-duplicate-chess-design.md for the full design.
Project Identity
A digitization of "duplicate chess," a four-player chess variant invented by Andrew
Freiberg (Seth's father — also the inventor of the blind-chess variant behind the
sibling blind_chess project). Four players (North, South, East, West) and four
boards (NW, NE, SW, SE); each player controls one colour on two boards and must play
the identical algebraic move on both. A captured piece leaves a frozen, capturable
"ghost" twin on the player's other board. Every individual board always remains a
legal game of orthodox chess.
This project is a local, single-operator sandbox/visualizer: one screen, all four boards, an engine that enforces the synchronized-move coupling, renders ghosts, and detects the endgame. Its purpose is to let the variant be seen and studied — the inventor's own point is that it cannot be understood from prose alone.
Current State
- Phase: spec complete; implementation not started.
- Repo:
git.sethpc.xyz/Seth/duplicate_chess. - Deploy target: n/a — runs locally (
pnpm dev). - Stack: Vite + Svelte 5 + TypeScript,
chess.js. Single package; engine insrc/engine/(pure, DOM-free, vitest-tested), UI insrc/lib/. - Next: implementation plan via the writing-plans skill, then build.
Conventions
- Inherits homelab conventions from
~/bin/CLAUDE.md(gitea CLI, conventional commits,.claude/handoffs/for session state). - The engine (
src/engine/) is DOM-free and the single source of truth for game state. The UI never computes legality itself. - Provisional endgame rules are marked PROVISIONAL in the spec — they are Claude's chosen defaults, not Andrew's rulings. Flag them if revisited.