Great game! Had a lot of fun playing it! I found jumping the walls at the second stage a bit difficult before. But now I developed a skill which is to press "w" and "space" together every time I jumped. Suddenly I turned into a great jumper!
There is a thing about audio. I actually got big audio issues with WebGL as well. I tried many different audio formats and settings in Unity. I finally re-export all my audio files as ogg files at a pretty low bitrate and in stereo. After import into Unity, I forced them all into mono and normalized. And all the severe problems seems are all gone. I wouldn't say it's perfect now, it's still a bit weird and definitely not as good as a Standalone build, but I hope it's helpful!
By the way, welcome to rate my game!