Haha I love that the bears just.. fall through! It would be hilarious if they had a little "drowning" noise.
I really, really love the layout of your CSS. It looks so nice seeing a Game Boy shell with the same green as the DMG. On mobile it comes out especially nice- like a Game Boy!!
The only thing for mobile (not web) is that I would prefer if I could use any button on the D-Pad to move left and the A button to move right. Sometimes the buttons are not what I want to press because I just want to limit each side to each direction. Does that make sense?
Edit: Actually, I think it's not about hitting the wrong input accidentally, it's that the buttons are small on my phone (iPhone X resolution). But, at the same time it looks really nice as-is (aspect ratio looks like a real game boy!). I suppose buttons will always be better than touch screen.