Thank you for the understanding. I have updated the HTML5 and Windows builds on the game page. This build has no gameplay changes, but drastically improves the fps.
For context, I was previously seeing fps dropping down to 10 by floor 15 (each successive floor is larger than the last, meaning it is more resource intensive.) And that was on the Windows build. The HTML5 build was far worse.
With this build, I still had 60+ fps on floor 15 on the Windows version, and a still-playable 30 fps on floor 25. I haven't been able to do full testing on the fps improvement of the HTML5 build, but I imagine it will benefit from the fixes as well.