Chess training that checks its own answers.
Puzzles, openings, and endgame drills, all checked by an engine. Import your own games, and Stockfish grades every move.
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Chess Gym started on August 22, 2026, with one rule: never teach a move that an engine hasn’t checked.
Below about 1500, games tend to turn on a hanging piece or a short tactic. So the gym trains those habits first. Missed puzzles come back on a schedule, drills are tested to be winnable, and your own games from Chess.com and Lichess get graded move by move.
The rule paid off early. When Stockfish first went over the puzzle bank, it flagged at least 15 puzzles that didn’t really win, or had a second answer that was just as good. I rebuilt them and made the check stricter.
I built it for myself first, then opened it up to friends with optional accounts. Six weeks and 169 commits later, it also has a Lab that teaches Jeremy Silman’s imbalances on a live board.
A wrong lesson is worse than no lesson. So an engine checks it first.
155 rated puzzles, from 400 to 2600, with a level picker. After each solve, a "Why it works" card explains the idea, and your rating moves.
A puzzle with two right answers teaches you nothing. A Stockfish check looks for one clearly best first move and a real win, and every line replays against the best defense on each test run.
You see a position from a real game. Play the last few moves in your head, type the mate in 3, then rebuild the final position on an empty board.
It trains calculation without touching the pieces. All 120 games are real, with both players rated 2001 or higher, and each one is checked to end in a forced mate in 3. The answer box forgives phone keyboards, so "rc2+" still counts as Rc2+.
Seven repertoire chapters, 36 lines in all, drilled one move at a time. Each move says why it’s played, what the other side wants, and which principle is at work. Eight more courses add 224 decision drills.
You learn the plan behind each move instead of memorizing a string of moves. The book reply plays itself after a short pause, and each line keeps its own review schedule, so one slip brings that line right back.
13 drills against an engine that defends well: basic mates, the Lucena and Philidor positions, opposition, and more. A stalemate or a draw by repetition counts as a miss.
If you fail a drill, the mistake is yours. Every start position is tested first, and seven drills get replayed by engine self-play on every test run.
Import games from Chess.com or Lichess by username, or paste one in. Stockfish 18 grades every move, from Brilliant to Blunder, with accuracy for both sides and the top three engine lines.
The engine runs on your own device, so there’s no server to wait on and no account to make. Your misses turn into puzzles that come back after 1, 3, 7, 16, and 40 days, so you end up drilling the exact mistakes you make.
Jeremy Silman’s book How to Reassess Your Chess, turned into seven lenses you lay over the board: pawns, squares, files, space, pieces, king, and plan. It comes with a nine-chapter course, a guided tour, and an X-ray for any position.
Every highlight is worked out live from the pieces, so it works on any position you bring, even from your own games. Every claim in the lessons is checked against that same analysis, and the lessons never quote the book.
#0e1013#1b1f26#f2f3f5#d2a24c#ebecd0#779556Inter for the app, a book serif in the Lab, and monospace numbers.
Borders instead of shadows. Gold only shows up in three places: where you are, the move to play, and the main button. Move grades always have a label and a symbol, so you can read them without seeing color.
White to move. One knight move wins something big.
Wrong moves get a hint. Like the real app, the puzzle keeps its name hidden until you solve it.
A piece slides from where it stood instead of blinking onto its new square. Make your next move mid-slide, and it picks up from there.
A puzzle shows only "Puzzle · 1500" until you solve it, because the name would give the tactic away.
Any checkmate solves a mate puzzle. A slower forced mate gets a free retry, with no rating loss.
The board takes all three, keyboard included. The promotion picker opens on the square itself, with the queen closest.
While the code loads, plain CSS draws an empty board, so the first thing you see already looks like the app.
Seven boards and six piece sets, based on the Nymzo Stanton Series 01, load before the first board draws.