TapChess ♞

A full game of chess against a computer opponent, built natively for the RayNeo X3 Pro AR glasses. Move a cursor around the board with right-temple swipes, click to pick up and place a piece — and when a move isn't legal, TapChess tells you why instead of just refusing it.

Built from the FABLE_X3_STARTER_GUIDE recipe and the TapBubbles/TapMemory lineage: 640×480 logical canvas, binocular side-by-side rendering, pure-black waveguide-friendly background, zero vendor AARs, zero permissions, zero binary assets — the whole chess engine, AI, and sound set are pure Kotlin, synthesized at runtime.

Controls (right temple pad)

Gesture	Action
Swipe ↑ ↓ ← →	Move the cursor one square (menus: navigate)
Click (temple tap)	Select your piece · place it · confirm
Double-tap	Open / close settings any time
Left temple pad	System volume (ignored)

Click your piece (it highlights with its legal destinations), swipe the cursor to a target, and once the ring around it fills — rest there about two seconds — click again to commit the move. That short dwell is a deliberate guard: the X3 temple pad isn't a perfect pointing device, and requiring the cursor to settle before a tap commits means a stray swipe can't fling a piece onto the wrong square. Click the same square to deselect, or click another of your pieces to switch. Also plays on a plain touchscreen with the same gestures. If a swipe direction reads backwards on your hardware, flip it in settings.

Why a move was rejected

Every illegal attempt gets a one-line explanation at the bottom of the board — for example:

• "A bishop moves only diagonally."
• "That would leave your own king in check."
• "A pawn can't capture straight ahead."
• "You're in check — that move doesn't save your king."
• "The rook's path is blocked."

It's a chess tutor as much as an opponent.

Computer difficulty

Five tiers, selectable on the title screen (swipe) or in settings:

Tier	Strength
1 · Pawn	Looks one move ahead and often blunders — a gentle start
2 · Knight	Two-move search, occasional slips
3 · Bishop	Three-move search, plays soundly
4 · Rook	Three moves + capture (quiescence) search, no mercy
5 · Queen	Four-move alpha-beta search with move ordering

The engine uses alpha-beta search with piece-square evaluation, capped by a per-move time budget so it always answers within a couple of seconds, running on a background thread so the UI never stalls while it thinks.

Speed mode

Turn on a chess clock in settings: 10:00 / 5:00 / 3:00 / 1:00 per side. Each player's clock ticks on their turn, the readout flashes red under ten seconds, and running out flags the game. Leave it Off for relaxed, untimed play.

Never lose your place

After the computer replies, the cursor jumps to your own king and its last move draws in as a fading, animated dotted trail with an arrowhead — so you always land oriented on where the action is. The game auto-saves after every move (and when you background the app), and resumes exactly where you left off the next time you launch it.

Settings (double-tap)

Difficulty · play as White/Black · speed mode · show legal moves · show coordinates · sound volume · swipe sensitivity · flip vertical/horizontal · safe tap · particles · frame cap (30/60 fps) · new game · undo move · resign · reset stats · Reset Settings (bottom of the menu, confirm-twice — restores every preference to default without touching your win/loss record or an in-progress game).

Menu navigation is discrete: one physical swipe always equals exactly one step, classified the instant your finger lifts — no drift, no lag, no accidentally skipping past the option you wanted.

Full rules are implemented: castling, en passant, promotion (with a picker), check, checkmate, stalemate, insufficient-material and 50-move draws. Wins and losses are tracked.

Build & install

cd ~/Projects/TapChess
./gradlew assembleDebug && adb install -r app/build/outputs/apk/debug/app-debug.apk

A built TapChess.apk also ships in this repo's root for a quick sideload without a build environment.

Toolchain: gradle 8.9 wrapper · AGP 8.7.3 · Kotlin 2.0.21 · JDK 17 · compileSdk 35 / minSdk 29.

X3 specifics honored

• Black is transparency: the board floats as neon light on the world
• No ar_mode meta-data (it would halve the display to one lens)
• Temple click read as a KEY event (KEYCODE_BUTTON_A/DPAD_CENTER); swipes classified by net displacement on finger-up, one gesture = one step, in every context (board, menus, settings)
• cyttsp6 (left arm volume pad) filtered out by device name
• RayNeo hardware detected by manufacturer/brand/product, not Build.MODEL (the X3 Pro reports ARGF20); binocular SBS auto-defaults on for it, no manual toggle needed
• Dwell-to-commit on moves; AI runs on a background thread; the sleep button auto-pauses into settings; the game persists after every move

A note on the controls

The X3 Pro's temple pad isn't a perfect input device — a swipe can land as the wrong direction or a stray click. Chess is turn-based and forgiving of that: nothing commits until the cursor has rested on a legal square, illegal placements are explained and harmless, and Undo Move is one double-tap away. Raise Swipe Sensitivity if the cursor feels stubborn.