Made it all the way to 10, I'm glad I wasn't stingy with the coins :) That last wave was a fun surprise.
The only thing I noticed was that the unit positions sometimes flipped their directions, and I had to spin my controller around to reposition them. Granted, they turn themselves, but at first, I was worried that their orientation would impact their performance.
This was a well-executed entry, and I had a lot of fun playing it. Fantastic job!