I'm on a Macbook Pro with an M1 Max chip and FF as my browser and while this is fun, the game became hard from a UX perspective to play once I hit the teens. My suggestion would be to remove the animations from the Artifacts, it feels like that's a huge source of the slow down.
I appreciate the feedback on the framerate (on, I'm assuming, the web version.) When I do profiling, the overwhelming majority of the time is taken up by the level rendering.
There may be more I can do to streamline that rendering code, but it will require a full rewrite of that rendering code at this point rather than minor optimization. I've already plucked all the low-hanging fruit I could find.