From what I hear this is an incredibly addictive game. I still have not played it enough to give a great opinion but what I have seen so far it is pretty good
do what elmst suggested (mass maze), then upgrad the middle towers to the final upgrade (sniper tower) one at a time. Sniper towers wins it easily when you got a huge maze.
someone posted this on my wow guild forum, its kinda repetative but still quite addictive somehow. I got to mission 6 and then got bored. what i did was mazed with the cheap vulcans then fully upgraded a few plasma and splash towers.
I'm on a page about incorrect corrections, and spent the better part of like two hours trying to get someone to understand that -5^2 = -25, not 25, and then that post had comments get reposted because that group is self sustaining, and that person was in turn trying to explain what I just explained to them. And I'm taking that as a victory