Live motion and tilt readout — does your phone's sensor keep up?
The page listens to two standard web APIs. devicemotion reports acceleration in m/s² along the X (left–right), Y (front–back) and Z (up–down) axes — including gravity, which is why a phone lying flat shows ≈9.8 on Z. deviceorientation reports the tilt in degrees: alpha is rotation around the vertical axis (compass heading), beta is tipping toward/away from you, and gamma is tilting left/right.
How to read it: hold the phone flat and watch the bars settle, then tilt it slowly onto each edge — the ~9.8 m/s² of gravity should slide from axis to axis smoothly. Shake it: the peak readout should jump well past 20 m/s². A sensor that freezes at fixed values, never settles near 9.8 on the down-facing axis, or drifts wildly while the phone is still on a table is faulty — and it will break auto-rotate, step counting and landscape games until repaired.
Why does iOS ask for permission? Apple requires an explicit user gesture before a page can read motion sensors. When you press Start on iPhone, Safari shows a "Motion & Orientation Access" prompt — tap Allow. If you denied it earlier, reopen the page and press Start again, or reset the choice in Settings → Safari → Advanced → Feature Flags / website data.
The numbers don't change when I rotate the phone. First check that auto-rotate itself isn't locked in your quick-settings toggle — that lock only affects the UI, but it's a quick sanity check. Then confirm orientation lock isn't enabled in the browser. If the beta/gamma tiles stay frozen on every axis while X/Y/Z move, the gyroscope is reporting nothing: that's a hardware fault worth a service visit.