Two quick tweaks Remove unnecessary HashShet and replace other HashSet with List. Adding to a HashSet seems to be slower than adding to the List

Optimize PreserveCounts and only recalculate when needed. Previously would recalculate preservecounts every Update call (~1 per frame), which isn't necessary when there's no tick. Might be some room to tweak, like doing these updates only when preserves change. Some measurements: This takes about 30ms versus the .25 ms with no preserve (then like .0002ms). When the map is filled up with preserve, about 35ms and 9ms. With a handful of cells, it's more like 0.8ms (before JIT optimizes most of it away).

Add timers for Simulation and various engines Starting to add additional timers for different stages of the process of updating in order to get more insight into what is slowing it down. The update takes 9ms, which is much longer than it used to. Engine-specific timers are coming later.

Disable extra sound effect outside of debug mode again.

Update TODO.taskpaper with performance things and some other issues I've previously forgotten to note.

Avoid exceptions on empty selections.

Ensure preserves don't overlap each other or contracted areas.

Update TODO.

Control audio via Options.

Switch over to SoundEffectsEngine Replace inline calls to play sounds to a dedicated engine. Having an engine will also make it easier to have audio settings.