We are seeking an experienced freelance mobile developer to finalize and stabilize a technically advanced Flutter-based audio and haptics synchronization system. The project involves integrating, testing, and polishing existing code for a cross-platform (Android & iOS) app that synchronizes metronome-based audio playback with waveform-based haptic vibration patterns. Key Requirements: - Integrate provided Flutter + Android code into a working build. - Validate and fine-tune audio ↔ haptic synchronization on Android. - Implement and tune iOS Core Haptics + Audio functionality. - Handle latency offsets correctly (positive & negative). - Finalize the Sync Test UI and ensure settings persistence. - Populate and validate the device test matrix. - Run basic real-device tests (Android + iOS). Ideal Skills and Experience: - Strong expertise in Flutter (Dart) development. - Native Android (Kotlin) experience with low-latency audio using SoundPool. - Familiarity with Core Haptics on iOS or willingness to learn. - Understanding of audio timing, latency, and scheduling. Deliverables: - Working Android & iOS builds with stable audio-haptics synchronization. - Persisted latency calibration settings. - Clean test-matrix export in CSV format.