As a prototype, there's definitely something here. It's a pretty short playthrough to get to the win condition, buy out all the upgrades, and start overflowing your savings, but it's satisfying all the same. I can see plenty of ways to expand on this: adding some stopwatches as multipliers, bonuses to slow down time, etc. It's definitely a pretty active game though, so it would have to consider some more idle options to expand the length too much, which could change the nature of the game. But it's a fun enough quick play to goof around with.