Chess Calculator
A trainer for one skill: calculating a sequence of moves before you play it. Real puzzles, a board that never moves, and the opponent's best defence included.
The idea
Tap a move and the piece slides. The opponent answers on screen. You never have to hold anything in your head, which is exactly the skill that decides games.
Here the position stays at the start for the whole puzzle. You enter your move, then your prediction of the opponent's best defence, then the next move, all from the same picture.
Tap the piece, then the square. No dragging, nothing moves. If the move is illegal in the position you're imagining, the app tells you at once.
Before you see the reply, say what the opponent should play. Finding the best defence is half of calculation.
When the puzzle ends, the whole sequence plays out on the board, so you see what you calculated.
Modes
Pick your move and the defence from a few candidates at each step. A warm-up that still makes you picture the position.
Enter one move at a time and predict each defence. A wrong move ends the puzzle, so you learn from the mistake instead of guessing on.
Enter the whole sequence, moves and defences, and submit once. Graded against the engine's full tree of defences.
Memorise the position, say you're ready, and the pieces disappear. Only the coordinates remain.
Feedback
Miss the move and you see the engine's refutation of what you played, the pattern you missed, and a short tip on how to see it next time.
Ask for a coach tip and a coach explains your specific mistake on this specific puzzle, grounded in the engine's analysis. The engine calculates; the coach only explains. Each tip links to drills that train what you missed.
Ratings
One puzzle rating hides that you see forks instantly and never spot a deflection. So every attempt updates a rating per tactical theme.
On the same scale as Lichess puzzles. It only moves when you're measured across all themes, so drilling one pattern can't inflate it.
Forks, pins, deflections, back-rank mates: each with its own number, and your defence accuracy next to it.
Sessions built around your weakest themes, with puzzles drawn near your level and never repeated too soon.
Your rating over time, a named level for where you stand, and a daily target if you want one.
Drills
Build drills give you a position as text and ask a question about it. Follow drills show a position, read you a few moves, and ask about the result. Drills count their own progress and never touch your ratings.
Puzzles come from the Lichess puzzle database, released to the public domain, and are analysed with Stockfish, free software under the GNU GPL.
Coming soon to iPhone and Android.