On the Level

Offline-first Android pocket toolset: a trustworthy level, angle meter, and calibrated screen ruler (Pro). Kotlin + Jetpack Compose, single module, no backend.

• BRIEF.md — the authoritative v1 product & technical brief
• AUDIT.md — audit of the brief; the amendments it lists are incorporated
• resources/ — concept board (visual direction)

Building

Open in Android Studio, or:

./gradlew assembleDebug        # build
./gradlew testDebugUnitTest    # measurement-math unit tests

Scaffold status

The project skeleton follows BRIEF.md §Sensor and measurement architecture. Implemented and tested:

• core/sensors — sensor selection (game rotation vector → gravity → low-passed accelerometer), device-frame gravity stream, and the pure measurement math: orientation mapping, two-sample per-mode calibration, EMA smoothing, lock hysteresis/dwell/debounce, display deadband. All unit-tested.
• core/settings — DataStore preferences and per-mode calibration persistence.
• core/billing — entitlement interface with a stub (free-tier) implementation.
• feature/level, feature/angle — live numeric scaffolds wired to the real sensor pipeline, with manual Surface|Edge selection, lock state, hold-to-zero.
• feature/ruler, feature/tools — static placeholders.

Not yet implemented (deliberately — see TODO markers):

• The tactile vial visuals and the spring-animated display value (value 3 of 3 in the brief); scaffold screens render the deadbanded stable value directly.
• Guided calibration flow UI (math and persistence are done).
• Edge-mode readout counter-rotation on the portrait-locked activity.
• Play Billing implementation of ProEntitlementRepository.
• Screen ruler measurement UI and per-display scale persistence.
• Audio cue, reduced-motion behaviors, preferences UI.