Love the fractal idea. Some improvements that come to mind:
- Being able to zoom in on your pieces in later stages
- Speeding enemies up for later stages, or an option for x6 or more speed. Even with x3 speed, the waves still feel slow.
- As the previous comment mentioned, the last few waves are a bit laggy (I only noticed this on x3 speed)
- The game feels a bit too easy, maybe lowering the $ drops could help?