To increase difficulty, have it randomly grant two purchases when upgrading. Buying 49 and it hitting 51. Evil.
I think your quick progress was before recent balancing. It's hard to test but I don't think it is too easy now. I'm even about to add more bonuses.
Likely. Adding another diamond didn't change the rate of progression on a restart. Takes a couple days to gain a credit now, which seems more appropriate. I can post the fresh 10001 diamond save if you want to test with it.
That is too crazy to test with :-) Also, bonus for bestiary unclocks was added just now.
