This game has a very interesting progression, but the MAX buy function seems to stop working with very large numbers and only buy 1 at a time no matter how much currency you have. Makes things a bit more tedious than intended.
I think it may also be nice to disable individual unlocked ball colours so they don't pollute the pool of balls that it cycles through; I've been focussing purely on the red balls and not unlocking later ones anymore so that I can drop the upgraded balls consistently, but I'm not sure how big of an advantage this actually is.
On a very minor note, the diamond shop says "Gold Upgrades" at the top, that might not be entirely right. :>