When motion sensors are not available on your device, you can follow these steps to enable them.

iOS

This only applies to iOS 12. You may need to remove and add the app to the home screen again for the changes to take effect.

Open settings and scroll down to find Safari:

Scroll down to find "Motion & Orientation Access" and toggle the switch on:

Android

Open this site in Chrome browser for Android and open the main menu by tapping the icon in the top-right corner:

In the menu that opens, tap Settings:

In the Settings, tap Site settings:

In the Site settings menu, tap Motion sensors:

You can now enable Motion sensors: