This is a pretty addictive game. I would say that the balancing how for how numbers scale should be calibrated, as it tended to explode really, really quickly once you unlock a new upgrade after lots of grinding earlier. Establishing the relationship between prestige currency and in-game currency as well as how multipliers interact (are they added or multiplicative?) would be nice too.
But overall, really fun. I found myself wanting to play just "one more round" each time. I think some of the upgrades would be better scaling non-linearly (such as the amount of extra time - rounds can get to be way too long long once you break past 1e20 or so).