Because the project is not on the Play Store, you must obtain the Android Package Kit (APK) file.

: Features numerous bug fixes, an idle screen dimming feature from Sonic Mania Plus

When you download the , you are not getting a hacked ROM or an emulator. You are getting the official 2011 engine, but patched to include:

Restores speedrun routes from the 1993 original that were altered in later ports.

: Go to your device's Settings > Security > Unknown Sources and toggle the switch to enable it. This will allow you to install APK files from outside the Google Play Store.