This update should fix the late-game performance issues when flames begin to spread. I had some underlying problems in my physics layer that were causing the engine to detect collisions in a very sub-optimal way, so when all those fire elements are on the screen checking for spread, it was making quite a mess.
I've refactored the physics layer completely, so you may notice some things move a little differently than before, and some things are a different speed than they were before. I'll be tweaking this moving forward to try to get back to the balance I'd found in the last patch, but for now I wanted to get this out so that everyone can enjoy the end-game without a supercomputer!