Yeah, I mentioned faster idle hitters, because they got to over -5 seconds (well, over -50 seconds before I noticed), which made idle hitters stop working in all stages. So you might want to test which benefits break the game if they get extremely high. I wrote which ones should be fine in previous post (more damage, more pixels), faster idle hitters are proven to need limit. I also suspect having 10k+ extra idle hitters might make game unplayable due to CPU not being able to keep up with that, but thats just my guess.
Faster idle hitters skillmine bonus breaking the game by being too high was second time I encountered this bug, first time it was cheaper upgrades skillmine bonus breaking the game by being too high (it made all upgrades unbuyable).
Oh, and this might help locating the bug, when I unlock the skillmine and choose the option out of the three offered, I assign workers to a field, however, when they finish that first field, they dont start working on the next one, but instead they work on some extremely easy virtual one, so I have to unassign workers by pressing X and assign them again and give them order in which they will work on visible fields with shift key and clicking, however, when they finish all fields, they resume working on that very fast to finish field that instantly regenerates (or there is infinite supply of them?). I am assuming all of this, because bonus is increasing very fast.
