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How the App Works

  1. Easily import your own chess games from various (online) sources such as or Lichess, or from your personal PGN files.
  2. Replay your blunders as personalized puzzles from your games and find better moves.
  3. Get support from the app in assessing your moves and recommendations of best moves based on chess engine evaluations.
  4. Learn from your blunders and improve your chess skills!
  5. Enjoy the app free and without ads.

Strategies to Avoid Blunders

While the chess blunder trainer app helps you to learn from your own blunders in past games, you will also need routines to avoid blunders in the first place. One proven approach is the Checks, Captures, and Threats (CCT) rule:

  • Checks: Check all checks that you can deliver to the opponent's king. Often, checks that do not seem to lead to anything, on closer inspection can open new ways of attack.
  • Captures: Examine all possible captures of enemy pieces. Sometimes, a capture can open up the board or remove a key defender, leading to a more favorable position.
  • Threats: Identify all threats you can make. A threat could be anything from threatening to win material in the next move to creating a strong positional advantage. It forces the opponent to react, e.g., by moving pieces, and may open new attack vectors.

In addition, make sure that you do not focus exclusively on your own strategy but actively take the opponent into account.

  • Understand the opponent's plan: Look at your opponent's last move and ask yourself, "Why did they make this move? What has changed in the position? What are they going to do next?"
  • Identify immediate threats: Use the CCT rule from your opponent's viewpoint to anticipate possible checks, captures, and threats. Make sure that have a counter to each of these moves, particularly if you are playing within opponent's half of the board.
  • Handle time pressure: When in time pressure, aim to simplify the position: exchange pieces to reduce complications, avoid overly complicated calculations


This chess software was developed as a personal project by Thomas Koeppen. The tool is available as a free Android app in the Google Play Store. Please reach out via with any feedback or questions!

Special thanks to Alex Baker, who published the chess logic package bishop and the chessboard visualization package squares for flutter. Without those, this app would not have been possible.

Release Notes