Its a really good game. I only made it to 47. Haha. Flamethrowers are the way to go.
Just completed it on hard difficulty (default). On the last level (51) I had 4 flamethrowers, 4 light towers, and 40 ice cannons.
Mak3ithurt, it actually ends on 51. Towards the end you definitely gotta spam light towers and electric towers. Very awesome game. Playing this with song number 2 is definitely the best game ever.
made it to wave 42 CLICK ON THE MIDDLE OF THE SQUARE TO THE LEFT OF THE TOWER U WANT TO UPGRADE! LIKE THIS _ _ |_||_| ^ |
Quite a fun game, hard to click on the towers to upgrade them. Pretty good!