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Turn every game
into a lesson.
Windmill turns raw engine output into something you can actually learn from. Import any game, get a report that names every mistake and shows the move you missed, then drill those exact positions until they stick.
Stockfish 17.1 in WebAssembly. Your games never leave your device.
Three ways to get better
Review, train, play. Everything talks to everything else: a blunder in your game becomes a puzzle, a puzzle opens on the analysis board, a bot game gets a report the second it ends.
Analyze
Import from PGN, FEN, a lichess link or straight from your lichess / chess.com username. Live multi-line evaluation with colour-coded arrows on every position.
Open the board → ✦Puzzles
An endless stream of rated puzzles from real games, filtered by theme. Plus a personal set built from your own mistakes.
Start solving → ♞Play
A bot with a personality at any rating from 400 to 2800. It plays favourites, gets moods, and misses things a human would miss.
Play a bot →Everything you need to understand a position
Powerful tools that turn engine numbers into insight you can use at the board.
Visual indicators
Arrows drawn on the board for the best moves, ranked and coloured by how much they lose. The evaluation rides on the arrow.
Game report
Brilliant, best, good, inaccuracy, mistake, blunder. Accuracy per player, per phase, an evaluation graph, and an estimated performance rating.
Coach notes
Every annotated move gets a plain-English sentence: what went wrong, what was better, and why it mattered.
Guess the move
Cover the game and play it yourself. Score points against the engine and see what the player actually chose.
Explode the position
See every candidate move at once, each with its own evaluation, to grasp the whole tactical picture in a glance.
Opening book
3,800 named openings identify the line you are in and show the book continuations. Add a lichess token for live win-rate statistics.
Mistake drills
Your blunders become puzzles. Windmill saves the position before every mistake and quizzes you on it until you find the right move.
Cloud-accelerated
Positions the community has already analysed come back instantly at depth 60+, while your local engine keeps digging.
Share & export
One link carries the whole game. Export an annotated PGN with evaluations and comments for your own database.
Train your tactics with real puzzles
Pick a theme: forks, pins, mates in two, quiet moves, endgames. Every puzzle comes from a real game and carries a rating, so your puzzle rating means something. Stuck? Ask for a hint, or open it on the analysis board with one click.
Solve puzzles nowPlay a bot that plays like a person
Choose a rating from 400 to 2800 and Windmill builds an opponent to match: a beginner who hangs pieces, a club player who drifts in the middlegame, a master who grinds small edges. When the game ends, send it straight to the report and see where it turned.
Play a botReady to find your best move?
No account, nothing to download. Open the board and start analyzing in seconds. Completely free.
Open Windmill