PPG Engine
Camera-based heart rate and HRV measurement. Fitzpatrick I–VI skin calibration with adaptive thresholds. Honest null when signal insufficient. C++ signal core — 94 KB.
BPM accuracy: <3 BPM MAE vs ECG
RMSSD correlation: >0.85
Frame latency: P95 ≤30ms
Reference: Polar H10
State Engine
Real-time classification: calm, fatigue, stress, recovery. Rule-based, no ML dependency. Circadian-aware. Optional SLM generates human-readable explanations in 4 languages — not required for core logic.
Classification: deterministic rules, <5ms
Text generation (optional): Qwen 2.5 0.5B (300MB)
Inference: <3 sec (text only)
Fallback: template strings, instant
Prediction: 2–4h ahead (logistic regression, after 14 days)
Intervention Engine
28 breathing protocols, 15+ acupressure points with illustrations, haptic guidance patterns. Adaptive — learns which protocol works for each user.
Selection: Thompson Sampling (MAB)
Context: time, circadian, season, lunar, TCM
Session: 3 min average
Evidence: PubMed 2020-2025
Learning Engine
On-device personalization. System improves weekly. Tracks what works, when, for whom. Stress prediction trains on personal data.
Training: weekly, during charging
Storage: 90 days, AES-256
Rollback: auto if model degrades
Inputs: HRV + calendar + tags + rhythm