As for the performance: I'm still surprised how bad it is compared to the console version I built.
I'll spend a lot of time optimizing and polishing the desktop and browser builds post this game jam.
Sadly, I have some issues with my workstation (Linus Torvalds really doesn't seem to want me to have 96GB of RAM) so it was hard profiling things at all.
Since the performance dips were accompanied by ominous screen flickering on my workstation and my workstation has video RAM issues that manifest themselves in this sort of screen flicker (again. Thanks, Linus Torvalds...), I assume a great deal of the performance issues are down to un-optimized textures.
While the browser version runs in 1366x768, the game's native resolution is 1920x1080 and some of the assets are even higher resolution that that.