Great achievement - nicely done, and nice idea!
I was I bit confused what was going on at first, I didn't see the Tutorial button for ages (it might be better along with the other buttons so you can't miss it). After that though, I really got into it - did all 30 waves. One thing that struck me was that as the the game progressed and your defences increased, the game got easier (but more hectic), so it would be good if it got more challenging instead to hard waves nearing the end.
That said, I really enjoyed it, the idea certainly sucks you in and before you know it, you've been playing for ages :)
One minor thing - I thought the joysticks that moves the arrow were broken to start with because there's quite a delay before it moves to the next square. Might be a good idea to make them more responsive.