Thank you so much, Doom x Christmas is exactly what we were going for!
Development-wise we (clearly) spent more time on visuals than gameplay, so the difficulty is quite unbalanced, it's not you!
I'm really happy you like the music, I was really struggling to make it at first, but then suddenly I just fell into the 'Angry Christmas' swing.
As for the browser slowdown issue, try disabling any ad/content blockers and let me know if it makes a difference (I use Brave browser and Brave shields interferes with WebGL games).