The game is fun for a short time.
However … with the current prestige system the other balls apart from the starting ball become obsolete quite soon … as do the upgrades.
If you want to keep exponential growth, you might consider using a smaller base like 1.1 or 1.2 instead of 2.
Here are a few ideas for (prestige) upgrades—in case you find a good way to keep the other balls and upgrades interesting:
- rotating perimeter (speed can be improved)
- bouncing/shaking perimeter (for even more chaos)
- free starting balls
- free starting levels of upgrades
- starting points > 0
- automation for purchasing upgrades/balls
- initial starting speed for newly bought balls
You could also add different perimeters. E.g. start with a triangle and after every prestige add another corner …