Has potential, but impossible to reach it.
I'm finding it quite impossible to beat either the second or third levels. Wave 44 is as far as I can get on the 2nd, and not even that far on the third. The first is the only beatable level.
The enemies become too tough and too many, and the financial cost of not dying is far too much. If the enemies gave more coins, it would be different.
Additionally, there are many crashing issues, as has been addressed in previous reviews. Please fix the crashing problem and the problem of the game being unbeatable.