I managed to get to ~ lvl 90 with castlemaxxing (see other comment), some feedback:
1) the physics really seems to be much less of an issue than in previous versions, well done <3
2) This uncovered two new bottlenecks:
- Units getting to position: this can take multiple minutes. Changing speeds/(un)pausing repeatedly helps, so I assume this to be some convergence issue. Might be solvable with either snap-to-grid (after a certain time) or changing the position-updating algorithm (better parameters/choosing a different one)
- Post-battle card selection: This can also take several minutes and is ultimately what killed the run (forced shutdown). I am not sure what causes this/what helps. If I'm to guess, computing card probabilities/going through all the discarded cards/something like that in some very demanding way.