Knight Fever technical documentation
How Chess: Knight Fever is built: a from-scratch engine, chess on a Möbius strip, Wi-Fi play with no server, and coaching and voice that run on your device.
Chess: Knight Fever is a chess app for iPhone, iPad and Mac, written in SwiftUI from one codebase. The parts that matter run on your own devices: the rules engine and its search, the bots, the coach, voice control, and Wi-Fi play between devices on the same network.
These pages explain how those parts work, for developers and for anyone who wants to check the privacy claims instead of taking them on trust. They describe Knight Fever 1.3.0.
Principles
- Free, with nothing locked. No ads, no subscriptions and no in-app purchases. Every mode and every voice and accessibility feature is available to everyone.
- No accounts. You open the app and play.
- Local-first. Games live on the device and, if you are signed in, in your own private iCloud. Signed out, everything still works on the device.
- No servers of our own. There is no Knight Fever backend. Wi-Fi games run directly between devices, and challenges arrive as local notifications, not push. The only outside services are Apple’s (your iCloud, and Game Center if you sign in) and a model download when you ask for one. There are no analytics, and the App Store privacy label is Data Not Collected.
- Rules before models. The engine decides what is legal and what is good. Language models only put its findings into words, and every AI feature still works without a model.
- Verified rule data. Lesson, puzzle and endgame positions are generated by scripts and checked with python-chess, never edited by hand. The Chess960 start positions were checked against python-chess for all 960 ids.
Ways to play
| Mode | What it is |
|---|---|
| Couch Clash | Pass-and-play on one device |
| Warm-Up Bot and Boss Fight | A friendly bot, and the engine at full strength |
| Bot Ladder | Five rungs of bot strength, from beginner up to the Boss |
| Bot Brawl | Two bots play each other while you watch |
| Wi-Fi Showdown | A game against another device on your network, joined by QR code or a four-letter code; Party Rooms hold up to eight devices |
| Endless | Chess on a Möbius strip, on one device or over Wi-Fi |
| Chess960 | A shuffled back rank, played pass-and-play |
| Sandbox | Set up any position and play it out against the Boss |
Games can be untimed (Classic) or played on a real clock with increments and flag falls: Bullet 1+0, Blitz 3+2, Rapid 10+5 and Long 30+0. Unfinished games save automatically. Finished games go to the Theater, where you can replay them move by move, open a Game Review, and import or export PGN.
The Dojo has a piece school, 35 lessons, puzzles and a Daily Puzzle, and separate trainers drill endgames, openings and board coordinates. Your stats (results, streaks, a local Elo rating, records by colour and by opening) are computed on the device from your match history, with ten achievements and optional Game Center leaderboards.
Where your data lives
| Data | Where it lives |
|---|---|
| Saved games, finished matches, your player name and theme | On the device, and in your private iCloud database (CloudKit) when you are signed in |
| Puzzle streaks and progress | On the device, mirrored through the iCloud key-value store |
| Stats and rating | Computed on the device from your match history; nothing extra is stored |
| An Endless game in progress | On the device |
| Club Chat history | On the device, encrypted |
| Downloaded AI models | On the device |
The pieces
| Part | What it holds |
|---|---|
ChessEngine | The position, legal move generation, the rules, SAN, FEN and position hashing |
ChessAI | The search: negamax with alpha-beta pruning and quiescence |
MobiusEngine | Endless rules, played on a 16-wide cylinder, with its own bot |
MultiplayerSession | Wi-Fi play over MultipeerConnectivity: lobby, rooms, chat, reconnects and spectating |
SecureWire | Sealed identity tokens for discovery and invitations |
ChatArchive | The encrypted, hash-chained, signed chat record |
ChessCoach, LLMService | The move coach and the assistant, and the chain of on-device models behind them |
ChessSpeech, VoiceMove, Speaker, SpeechListener | Spoken moves and voice commands |
MatchStore | Saved games and history, on the device and in your private iCloud |
Where to start
- The engine: the rules, the search, the bots, Game Review and Chess960.
- Endless: the Möbius geometry, and the cylinder that keeps it simple.
- Wi-Fi play: joining, Party Rooms, spectating, and what protects moves, identities and chat.
- Coaching and accessibility: the model chain, the Dojo, voice and VoiceOver.
- Roadmap: what is designed, planned or in progress but not shipped.
Want the short version first? The Knight Fever showcase has a Möbius board you can explore in the browser, and the app page has the listing.