Endgame Study — a chess trainer

Play a bot at your level, then get a real breakdown of what went right and wrong.

Right-click and drag on the board to draw an arrow, right-click a square to ring it. Hold Shift, Alt or Ctrl while you draw for red, blue or orange. Left-click clears. Press and hold a square, then drag to draw an arrow. Hold and let go without moving to ring the square. Tap the board to clear.

Match setup

Set up a match and start playing.
Pick a strength and a colour, then start. Your moves will appear here.
Finish or resign a game to unlock its analysis.

Puzzle drills

These are pulled from moments in your own games where you (or the bot) let the position slip. Find the better move.

No puzzles yet — play and finish a game first.

Endgame drills

Set positions played against Stockfish at full strength. It defends perfectly, so sloppy technique gets punished every time and you can't luck into a win. Work down the list — the mates come before anything else.

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Blunder check

Your reviews keep saying the same thing: you left a piece capturable. That is a scanning habit, not a knowledge gap, so it gets trained directly.

Press Start. You'll get a position with you to move — tap every one of your pieces the opponent could take right now for free or for profit.
Ready.
No games saved yet. Finish a game and it'll show up here.
Import games

Paste PGN from chess.com or Lichess, or fetch a month straight from chess.com. Imported games get the same engine review, puzzles and progress tracking as games played here.

This build

Running build: —

The September 2026 design pass is layered on top of the original styles rather than replacing them, so Classic puts everything back exactly as it was. Saved per device.

If this doesn't match the build you just uploaded, your browser is showing a cached copy. On iPhone: close the tab, then reopen the page — or load it once with ?v=2 on the end of the address to force a fresh fetch. A stale copy will keep producing the old, wrong review numbers.

Game analysis backend

Playing, puzzles, the handbook and the replay boards all work offline with no setup. Only the written coaching review needs to reach Claude. Pick one option below.

Local mode analyses every move with Stockfish and writes the review itself. Nothing below is needed for it.

A small backend you host that holds the API key server-side. Nothing secret lives in the browser.

Stored in this browser's local storage and sent straight to Anthropic. Fine for personal use on your own devices — but anyone with access to this browser profile can read it, so don't use it on a shared machine and don't hardcode a key into a public site.

Your data

Games and puzzles are saved in this browser. They don't sync between your phone and PC — each device keeps its own library.