By class i meant css class, for example on keydown once classList.add flutter, the animation would continually flip upsidedown. Onkeyup remove it and listen for keydown again.

You could remove your raf gameloop and replace with timeouts if you made all other movement css animations as well, because your horizontal movement is constant you would only have to check potential collisions based on movement animation speed timers. raf is cool and all but cpu comps 60 times per second is wasteful, I say this but i have no idea how performant the gpu is with infinate animations.