Chess puzzles built from your own games
Most puzzle sites serve you famous positions or games played by strangers. Blunderland does the opposite: it takes your games, finds your mistakes and hands them back as exercises. You only train on your own blind spots.
Generic puzzle or personal puzzle?
A classic tactics puzzle trains pattern recognition: fork, pin, double attack, mate in two. That is useful and worth doing.
But it has a limit: nothing guarantees the motif you are drilling is the one costing you games. You can grind two thousand mate in two puzzles and still hang a bishop every third move.
A puzzle taken from your own game does not have that flaw. The position really happened, you really played the wrong move, and remembering the game makes the correction far more memorable.
How the puzzles are generated
The process is fully automatic and takes four steps.
- Your recent games are fetched through the public Chess.com or Lichess API, from your username alone.
- Each game is analysed by Stockfish, compiled to WebAssembly and run in your browser: no game is ever sent to an analysis server.
- Every move where the evaluation drops by at least 300 centipawns becomes a blunder candidate.
- The position just before the mistake becomes a puzzle, with the correct move as its solution and a tactical motif attached.
Spaced repetition, so it sticks
Solving a puzzle once is not enough: the correction fades within days. Blunderland therefore applies the SM-2 algorithm, the same principle as flashcards.
A puzzle you solve comes back later and later. A puzzle you fail comes back soon. The home screen simply shows what is due today, with nothing for you to manage.
What it costs
Nothing, and there is no paid tier hiding behind that. No daily puzzle cap, no analysis depth reserved for subscribers, no mandatory account.
That works because the analysis runs on your machine rather than our servers: one more player costs us nothing.
Who it is for
Players between roughly 800 and 1500 Elo, whose games are still decided by tactical mistakes rather than positional subtleties.
The tone is deliberately mocking, never humiliating: own your blunders, laugh at them, then fix them.
Frequently asked questions
Are the puzzles really free?
Yes, entirely. No paywall, no daily limit, no reserved features. The analysis runs in your browser, so it costs us nothing.
Where do the positions come from?
From your own Chess.com or Lichess games, fetched through their public APIs using your username. Each puzzle matches a move where you genuinely lost at least 300 centipawns.
Do I need to create an account?
No. Without an account your puzzles live in your browser. An account only lets you find them again on another device.
Which chess engine is used?
Stockfish, compiled to WebAssembly and run in a Web Worker in your browser. Your games never pass through an analysis server.
How long does the analysis take?
A few dozen seconds for a handful of recent games, depending on your machine. Progress is shown while it runs.
Does it work on a phone?
Yes. The site is an installable web app (PWA): add it to your home screen and review offline.
Generate your puzzles
A username is all it takes. We analyse, we find your blunders, you replay the positions.
▸ Analyse my games