Happened to me too and had to stop for a moment because of the flashing 😅. I don't know what happened with the framerate, maybe linux stuff?
Viewing post in Riko of the End [GBJAM14][EN/日本語] comments
I figured out the cause is related to the camera smoothing and extremely low FPS (<10). Make sure hardware acceleration is turned on in your browser, or pull a Todd Howard and try on a better PC? I was able to reproduce it exactly as you get it by throttling CPU in chrome, and removing the throttle fixes it, so it's directly tied to fps.