Interactive solver for YACPDB chess problems with move validation, Stockfish hints, and full solution display including tries and variations.
Over 575,000 problems: direct mates (~406,000), helpmates (~85,000), selfmates (~53,000), studies (~32,000), and retros (~1,500).
Live site: arcade.chessproblem.org
© 2026 ushiyutvj. All rights reserved. The source is published here for reading and reference only; copying, redistribution, or use of this code in another site or product is not permitted without the author's written permission.
- Solve direct mates, helpmates, selfmates, studies, and retro problems on the board
- Move validation against the solution tree
- Stockfish-powered hints
- Solution playback with clickable moves
- Rated Mode — Glicko-2 matchmaking that picks problems near your skill level, with separate pools for direct mates, helpmates, and selfmates. Perfect solve = rating up, any mistake = rating down
- Review Mode — FSRS-4.5 spaced repetition for problems you've played in Rated Mode. Reinforces weak spots on a schedule
- Analysis board — a free board for thinking while you solve: move any piece anywhere, both colours, nothing checked. Your answer still counts only on the real board
- Play vs engine — continue against Stockfish when YACPDB's solution stops early, or play out a study
- Themes — a guide to the classic ideas (Battery, Zugzwang, Grimshaw, Novotny, Plachutta, Model & Ideal mate, and more), each explained on a prize-winning example. After you solve, the idea inside that problem is explained on a marked-up diagram
- Twin problems: every twin's position and solution
- Helpmates with several solutions: find them all
- Filters by theme, stipulation, piece count, year, and award
- Search problems by composer
- Bookmarks and solve history
- Daily problem, with an archive of past days
- Dark mode
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- React + TypeScript + Vite + Tailwind CSS
- Cloudflare Pages + D1 (SQLite) + Workers
- Stockfish WASM for analysis