This idea's amazing! There is little better than when someone takes a concept and replaces the main component with a llama; the concept here, of course, referring to towers.
The gameplay here worked really well, though the fact I'm using a laptop to play it probably didn't do it justice. I can imagine the game would not only be alot easier, but would feel alot smoother had I used a mouse to play, so I'm trusting in that fact. Having played on a laptop, however, the controls worked well, and I was able to play through the eighteen levels present within the main story, though at times having to swipe the track pad to quickly shoot a pirate spawn on the other side of the screen could prove needlessly challenging, through no fault of your own.
Also, I think that the difficulty curve here was a little steep. The first few levels were painfully slow and easy, and then as they got into the 10's, the enemies would come thick and fast, and the difficulty seemed to change drastically. I know it's tricky to get the difficulty curve just right, and in this case you seem to have just missed the mark, with the game sometimes feeling a little unforgiving.
I had no quarrels with the graphics; in fact, I liked them! They reminded me alot of games such as 'Earthbound' on the SNES, and as such looked very professional. It's easy to tell that alot of work has gone into this game, and it has most definitely paid off.
The music was very nice, and fit each new locale within the game perfectly. I also really liked the upgrade system! It all worked very well, and made the game hugely enjoyable.
In conclusion, the game's great! Other than a slight issue with difficulty, there was little to nothing wrong with the game. But where DID that llama get his trampoline?