Guess the hinge angle. The phone is the controller: fold it until you think you have hit the target angle, then tap to score.
Built with Ionic Angular, Capacitor and @erkamyaman/capacitor-foldable. Runs on iPhone Duo (iOS 27.1 or later) and on Android foldables with a hinge sensor.
Meter follows the hinge live. Game names a target to fold to, then scores the measurement. The protractor's pivot sits on the crease, so the phone's own hinge is the instrument's.
The dashed arm shows where the phone actually was. Flat at 180 degrees the instrument lies straight across both pages.
- Game. Each round names a target between 30 and 165 degrees. Fold to it, tap Measure, and the round scores on how close you were. The target arm stays put, a dashed arm marks the angle you folded to, and accuracy carries over as an average across rounds.
- Meter. The live hinge angle on the same dial, with nothing to score. Useful for seeing what the sensor actually reports while you fold.
- Fold the phone shut and the app asks you to open it: there is no hinge angle to read on the outer display, so the tab bar goes away and a prompt takes the screen.
The dial is a bevel protractor drawn in SVG, and its pivot is placed at the middle of the fold the plugin reports, so the arms sweep across both pages. How long a move takes comes from how far the arm has to go: 140 ms plus 4.4 ms a degree, capped at 900 ms, which is quick for a nudge and unhurried for a sweep across the scale.
| API | Used for |
|---|---|
isDeviceFoldable() |
Tell a foldable from a phone that can never play. |
getHingeAngle() and hingeAngleChange |
The live angle behind the dial and the score. |
getFoldState() and foldStateChange |
Whether the app is on the display with the fold, which decides between the game and the unfold prompt. |
getFoldState().hingeBounds |
The crease's position, which the dial's pivot is placed on. |
The hinge service also polls every 300 ms and refreshes on visibilitychange, focus and resize. iOS pauses the web view while the app moves between displays, so events can be missed while the phone is folding.
The tab bar itself is native, through @capgo/capacitor-native-navigation. Both modes are views of one instrument, so the bar swaps the view in place rather than routing: routing mounted a lazy page on every tap, which showed as a blank frame and a sideways slide.
On iOS 26 and later the system owns the tab bar's tint, so the icons carry their own colours and the window is tinted in SceneDelegate.swift.
npm install
npm run build
npx cap sync
npx cap run ios # pick the iPhone Duo simulator, Xcode 27.1 or laterFold the simulator from DeviceHub, or use hinge to drive the angle from the terminal:
hinge sweep 180 60 2Xcode 27 ships the simulator inside DeviceHub.app rather than Simulator.app; hold Option over the hinge slider for finer control.
MIT