Oh, and it would really help to know some details about your system, so I know what to target. Would you mind sharing your browser and roughly what device you're running it on?
That machine should be absolutely crushing Grimward. I've made some performance improvements, but after checking the game in Firefox on my machine, I feel a very clear difference in performance: Firefox performs noticeably worse than Chrome. I'll spend some time in Firefox and see what can be improved, as that will likely make the game feel better in Chrome as well.
This was very useful feedback! I really appreciate it and I'll do my best to fix it.