Caffeine Tracker
Models what is actually in your bloodstream, not how many cups you drank. Everything stays on your device.
Open the app Watch the 43-second tour →Install on Android or desktop: open the app, then use your browser menu → Install app. It gets a home-screen icon and works offline from then on.
On iPhone or iPad: open the app in Safari, tap Share → Add to Home Screen and keep Open as Web App switched on. Always start it from that icon: Safari can clear a website's data after a week without a visit, but the Home Screen app keeps its own.