This behavior has now changed for me. With Safari and Mobile Safari, Centipede 416 is now always grey, and the controls do not control the unit’s output.
What I’ve seen:
Browsers with the problem
Safari 15.4
Mobile Safari (iOS 15.4)
Firefox 97.0.1 (macOS)
Firefox Focus 98.1 (iOS)
Firefox Daylight 98.2 (8475) (iOS)
Chrome 100.0.4896.56 (iOS)
Browsers that work
Safari 15.3
Chrome 100.0.4896.60 (macOS)