Like EIdema said, a tutorial is extremely needed. You can survive without one.. its just damn hard.. It looks similar to Age of Empires from the start to me :)
medics... OWN!!
I increased my speed at first for like 3, then health to 5 then speed to 7 then all health.
Stay in the back near towers and just help provide fire and health for teammates
The song is funny ahah. Henshin, you only need common sense to think of where they are needed. That big gap in between your other turrets that leads right to your power sources and fortress? Yeah I think a few weapons there would be good. Ghez, nuke plants are good too >:) Level 8 is extremely easy, if you think about what you would need for the basics to stay alive, all of that stuff is transferred to the other base.
Its like L4D(sorta cuz of those special zombies)+COD:WAW's Night of the Living Dead combined into a flash game. Cooool. Multiplayer update would make it my favorite game for sure. DItto about what warrioreriq said about the ratings. 5/5 pity rate! (woulda been 5/5 anyway :P)