the aspect ratio of your embed is used to set the orientation of the device. Which game is this, I can take a closer look to see if it's too aggressive (for example, you have a square game)
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Cheers, it's here: https://cloakedninjas.itch.io/ruff-interview
It seems to be isolated to Android Chrome. Using chrome dev tools and simulating a mobile device doesn't affect it strangely. Perhaps something to do with the Fullscreen API ?
I noticed something similar and submitted this issue: https://github.com/itchio/itch.io/issues/881