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Guide : Puzzles & Ratings

Puzzles used for the Blitz and Memorize exercises are generated by heavy computer analysis from real games. Solutions are based on the strongest line of play as calculated by the computer. The first move made by the opposition is the move made in the actual game and so is not always the strongest one. However you still need to find a move that will capatilise on the position.

When there is more than one strong move available, the correct solution is deemed to be any of the strong moves that are available. The computer evaluation for each of the available moves is shown in the solution.

Given that computers do not have the power to exhaustively search positions will inevitably mean that some puzzles may not have had exactly the correct solutions calculated. Moves listed beyond the bolded solution are less likely to be optimal as the computer analysis finds it harder to find the best lines deeper in the search and are posted for completeness.

If you find a puzzle with an incorrect or unduly harsh solution please post us the the puzzle number, whether it is a blitz or memory puzzle and the move(s) you think have been mis-evaluated. We aim to update these periodically, should the need arise.

Ratings are applied for Blitz performance. Both the user and the puzzle are rated based on the public domain Glicko rating system devised by Mark Glickman. Ratings are not applied to the memorize problems as they will inherently get easier and easier as people memorize more of them. Blitz puzzles are much less prone to this.

Ratings start at 1500, and have an RD (rating deviation) of 350. The RD is a number representing how accurate the rating is - the lower the RD the more accurate the rating. As you complete more puzzles your RD will lower and your blitz rating will adjust according to whether you got the correct answer, how long it took you to find it, and how accurate your own and the puzzle's rating are.

If you are registered, the puzzles' ratings will be adjusted in the same manner as your own, so the more puzzles you attempt the more accurate they become. Over time your RD will increase if you are inactive, reflecting the nature that your rating is no longer as certain. A user's RD will never drop below 20 so a reasonable level of rating improvement can always be achieved.