I've come across a few things that maybe aren't working as intended and some changes that could make the game easier to understand.
Possible bug: The +XP text doesn't show every 7 seconds for some of my keys.
Background: I noticed this 20k seconds into the bonus round and haven't had a chance to do more testing. I'd guess that I have 30-50 keys of wisdom, all but a couple in an iron man. The couple others are farther away and I've noticed that their +XP text only shows up about half of the time (not every 7 seconds, time between text is either 7, 14 or 21).
Possible explanation: it might be that with the large number of items in iron man, something is going on. Maybe all of the XP is added, but there's a limit on the amount of text on the screen or something. I'm not sure.
Maybe not working as intended: hydra arrow does much more damage than should be possible by the description.
Possible explanation: the description says poison is added every time the tower deals damage. This might mean that the hydra poison triggers its own effect. So each time the unit takes poison damage, another poison for 20% + 0.02%/level is added.
Suggestion: to make the game easier to understand, it would be nice if various chances were shown with how the stats affect them. E.g. as the shadow gets more levels and luck, it could show the current chance to adapt.
This could just be an updated number, but that wouldn't show how it is affected except by trial and error. Another option is to color code all your stats. If luck were pink, then a shadow with 100% luck would show a pink +3% next to the adaptation chance (I think that's how it works, but I don't know). Right now I'm not sure if this would affect anything but luck.
Suggestion: add counters for other tower specific things, e.g. money stolen by a pickpocket, research done by the scientist, etc. This would just be a neat thing to see. Mostly cosmetic. Maybe for the black widow, it would show how many items were found because her bonus was applied (not sure if you calculate that separately, so maybe not this one).
Question: how do slows combine in this game? Does only the strongest one count? My main question is about the spider vs frozen daemon