Great game! I love the way the towers are placeable items from your repository, rather than purchasable ones. The mechanics, the art, and the music were excellent. Well done!
I was reading some comments below, so I wanted to share that you can actually beat the game without ever buying the cannoneers (I did it as a test). You can also beat the last level without ever using your cursor attack (just make sure to max everything else, first). Here is the last level layout with no cannons and you just watching :)