Version 1.2 is out on the App Store
A chess coach who shows you the why.
Sealed Move is a chess coach on your phone. A real engine makes every judgment; a coach who talks like a person explains it. No invented lines, no confetti. Just your games, understood.
Download on the App Store iPhone and iPad · iOS 17.0+
Free to download and free to keep playing. The optional Pro Coach subscription is $5.99 a month, with the first 7 days free.
Tap the coach's words
Every square, piece, and move the coach mentions is live. Tap
f7 and the board shows you f7. Tap a move and the annotation
pen draws it: the same red arrow a coach reaches for at the demo board.
You never leave the conversation to find out what a word means.
Italian Game · you're White
Coach
Your and the knight are both staring at , the softest square in Black's camp. If you're tempted by , count the defenders first.
Tap anything the coach names: squares, pieces, moves.
A lexicon with moving parts
When the coach names a fork, a skewer, or a Najdorf, the word links into the Lexicon: a textbook definition, where the idea wins, where it goes wrong, and the pattern played out on an animated board instead of a paragraph you have to imagine. Openings, tactics, and concepts, every demo line checked by the engine before it shipped.
Tactic · Lexicon
Fork
One piece attacks two or more enemy targets at the same time, so the defender can only save one. Knights are the classic forkers because their attacks can't be blocked, and a fork that hits the king forces the reply.
- Wins material by force when one target is the king
- Knight forks are invisible to players who only watch lines
- A fork on two defended pieces wins nothing; check the landing square
- Setting one up often telegraphs the idea a move early
The royal fork: check first, collect the rook second.
Tactic · Lexicon
Skewer
The pin's reverse: a valuable piece is attacked and forced to move, exposing a lesser piece behind it on the same line to capture. Skewers through the king are the deadliest: the move is forced, and whatever hides behind falls.
- The front piece must move, so the gain is forced
- Devastating in endgames where kings and rooks share lines
- Needs an open line; one blocker defuses it
- The targets must actually be aligned, and engineering that is the hard part
Check drives the king aside; the queen behind it is taken.
Tactic · Lexicon
Discovered Attack
Moving one piece unmasks an attack from another behind it, leaving the moving piece free to create a second threat anywhere on the board. When the unmasked attack is check, the moving piece's threat lands untouched.
- Two threats from one move; the defender can rarely meet both
- Discovered check makes the front piece effectively invincible for a move
- Requires a battery to be assembled in advance
- An alert opponent will trade off or block the masked piece early
The knight steps away with tempo, and the bishop's check pays for the rook.
Tactic · Lexicon
Smothered Mate
A lone knight mates a king completely boxed in by its own pieces. In the full classic (Philidor's legacy), the queen is sacrificed on g8 to force the rook to smother its own king, and then the knight delivers the famous blow.
- The knight's unblockable attack is the only piece that can do this
- The queen-sacrifice version is completely forcing once it starts
- Requires the king's escape squares to be exactly occupied
- Spot the pattern too late and the sacrifice is just lost material
Every escape square taken by the king's own guards.
A hint, never the answer
Mid-game, the coach won't hand you the move. Play a quiet move in a loud position and it tells you what kind of thing you're missing, never which. The eval is the engine's, the nudge is the coach's, and the find is still yours.
Two Knights Defense · move 6 · you're White
Your move. 6. d3
Coach
d3 is the move you make when nothing is happening. Something is happening. Two of your pieces are already aimed at the same soft square. Count the forcing moves before you go quiet.
6. d3?! · eval +2.4 → +0.6
The hint points. It never spoils the find.
Share the game as a video
Your best games deserve an audience. Export any finished game as a vertical video: pick the stretch that mattered on the review timeline (the whole game, or just the five moves where it turned), choose the coach's red arrows or classic square highlights, and let the coach's notes hold on screen at reading pace. The clip ends on the game's report card, sized for a phone and ready for the group chat.
The engine judges. The coach explains.
Chess apps love to tell you a move was a mistake and leave you staring at an engine line. Sealed Move splits the work the way a real training session does: Stockfish makes every factual claim (evals, best moves, tactics, opening names) and the coach turns those facts into plain speech. The coach never analyzes the board on its own, so it can't invent a variation. If we don't know, we say so.
An opponent who plays like a person
Practice games run against Maia, a neural network trained on millions of human games at fixed rating levels, so your opponent blunders the way people blunder, not the way a handicapped engine does. As you improve, the level moves with you, and the coach tracks which concepts you've actually mastered rather than how many puzzles you've ground through.
Built for adult improvers
You've watched the recaps. You know you're not becoming a grandmaster; you want 1400, then 1600, and to finally stop hanging knights. The coach laughs with a blunder, never at you, cites the eval instead of cheerleading, and skips the streak-confetti economy entirely. Chess is already a game; it doesn't need another one on top.
Why "Sealed Move"?
When tournament games paused overnight in the adjournment era, you wrote your next move in secret, sealed it in an envelope, and both sides went home to analyze. Secret preparation, deep analysis, the resumed game: that ritual is exactly what your coach does between your moves.
Get Sealed Move
Out now for iPhone and iPad, iOS 17.0 and later. Two ways to start, and both come with the full game, the engine, and your coach.
Free Coach
Free
- Runs entirely on your phone. Nothing leaves it.
- Engine-checked moves and instant feedback.
- Free forever, not a timed demo.
Pro Coach
$5.99/month
First 7 days free. Auto-renews monthly until cancelled in your App Store settings.
- Our sharpest coaching, powered by cloud AI.
- Deeper explanations and richer game stories.
- No account and no sign-up. It just starts.
Download on the App Store Tell us how it went
Positions only go to the cloud on Pro Coach, and only after you say yes. Read the privacy policy or the source before you decide.