I had a great time playing your game!
The UI and UX are really well done, with everything being easy to understand and navigate. The tower and character designs are fantastic, and I really enjoy how the towers rotate to face the enemies. The fast forward feature was also a great touch and helped speed up gameplay during tougher waves.
It would be great to have some more visual effects when enemies are hit, such as them flashing red or adding some VFX to make those moments feel more impactful. I also found that you could lose early on by spending all your cookies before the round had started.
An instant retry button would be a nice feature, making it easier to jump back into a new round without going through the start menu. I also accidentally placed a tower while interacting with the UI for accepting a challenge.
Lastly, I felt that the starting money was a bit generous, making it easier to place a lot of towers early on and not worry about enemies for a while. A bit more balance in this area could help make the early waves more engaging.
Overall, the game is a lot of fun, and with a few small adjustments, it could be even better. Great job and keep it up!