Good game, you need to fix the bug were you can't die, but i liked how you could upgrade a unit in more than one way and how many upgrades for each "path" there was. so fix that bug and bring on the badges.
I like it, the graphics are good, i like how the towers change, and the music is great, the only things that i would change is take up the damage on earth towers, take up the rate of fire on the ulimate towers, and make a couple different game modes (easy, normal, hard, super hard) with easy being just a little bit easyer than it is right now and normal being a little bit harder.