Just some advice for starting out: Use the Druid until you unlock more advanced creatures. The Druid has an incredibly fast ranged attack and a heal, so if you're careful you'll never die.
After a long fight it's down to just one of my guys and one of the enemies. We're on the same planet. I walk up confidently and pull out a Sniper Rifle. I take aim and fire directly at his head. It flies through his head and does no damage. He pulls out a normal missile and kills me. I lose. :'(
"SIR!! We have detected a tank that seems to be indestructible! Luckily it has no weapons and can only hurt us when we drop bombs on it! What are your orders." "HIT IT WITH EVERYTHING WE GOT :D!!!!"
I find it slightly disturbing that the survivors are just hanging around with zombies in houses until you enter. They're friends until you walk in meaning it's YOUR FAULT that that we have to kill them. Think about THAT for a while ;)
Good game, besides what's already been suggested, making some towers a little smarter would be nice. When my Freezing Towers start firing on a group of zombies, they don't try and slow them all, they focus fire on the one in front and many don't get slowed until later.
Hey man great job on the game :) I appreciated the creativity and time you clearly put into it. Even if the average rating you're getting isn't very high, it's not like you did anything wrong, there are just lots of dumb people rating your great game low.
There's a multiplayer game, CycloManiacs Racers, at www.turbonuke.com.