Thanks for feedback. The xp boost is an interesting concept, I was thinking about that as well, but I don't think this is meant to be played character after character in the first place. I'd imagine most people would switch up characters, so by the time you fully finish one it might not matter much. Also, unless you're reporting a bug that I'm unaware of (I just tested the feature to be sure), the idle element should work whether window is active or not (I will fix the freezing window issue next update). Behind the scenes, when an "upgrade" pays, it compares the last time it payed to the current time, so if you click out of game leave for an hour you would have 1 hours worth of currency added at once when you click back. Same with switching to different characters, and same with exiting game, the save file also stores when the upgrade payed last, so the moment the game loads you get all the currency from when the game wasn't open.