Its a little too slow, Even on FF. Plus it is way too easy to fill the entire board with towers as they are very cheap. Perhaps it would have been better if the price of towers went up after each build? Either that or you should have made the enemies give you less money. Also the game lacked difficulty, Even on *Hellish* and to top it off the game gets very redundant and old as there are very few enemy types and even less towers to choose from.
The style was good and the animations ran smoothly. I also like the song that plays in the background. Over all the game was rather fun at first and it had great Potential to be quite awesome. Maybe try another one similar but with upgrades and more enemy types. Add a little challenge to it as well.