Caffeine mg: Half-life Tracker

Caffeine mg is a one-tap caffeine tracker that visualises remaining body caffeine and the
time it drops below a sleep-friendly threshold using a half-life decay model.

"Can I have one more coffee this afternoon and still sleep tonight?" — that's the question
this app answers.

■ Who it's for
- Daily coffee or energy drink consumers
- People whose afternoon caffeine affects sleep
- Users who prefer no ads and one-time purchases
- Login-free tracking with caffeine records stored on device

■ Main features
- 50+ preset drinks (coffee, energy drinks, tea, etc.)
- Custom drinks with caffeine content and serving size
- Tap to log "now", long press to set the time
- Today's total intake and remaining allowance (400mg default)
- Half-life decay simulation
- Home screen widget for one-tap logging
- Siri / Shortcuts support
- Last 7 days of history

■ iOS 18 features (Pro)
- Live Activity + Dynamic Island for body caffeine + sleep-friendly time
- Lock Screen Control + Control Center for one-tap logging
- Action Button on iPhone 15 Pro and later
- Half-life simulation chart

■ Pro (one-time, JPY 370)
- Unlimited custom drinks
- Live Activity / Dynamic Island
- Lock Screen Control
- Action Button integration
- Full history + CSV export
- Medium / Large widgets

■ Why we made it
- Free to start (50+ presets + 3 custom drinks)
- No login, no account
- Caffeine records stay on device; anonymous usage events are optional
- No subscription. Pro is one-time only.
- Zero ads.

■ Science
- Daily upper limit 400 mg (WHO / FDA / EFSA / Health Canada / Japan MHLW Sleep
Guidelines 2023 consensus)
- 50 mg "sleep-friendly residual" threshold per Japan MHLW Sleep Guidelines 2023
- Default half-life is 5 hours (individual range 3-7 hours)
- All thresholds adjustable in Settings

■ Requirements
- iOS 18.0 or later (for Live Activity / Lock Screen Control / Action Button)

This app is intended as a caffeine intake tracker. It does not provide medical advice,
diagnosis, drug-interaction checks, or individualised guidance for pregnant users, users
with cardiac conditions, etc. Please consult a doctor or pharmacist for health decisions.