First of all cool game, really liked it
It'd be better if there were more visual changes though, eg. different animation for bullets hitting your shield as opposed to armour, slight changes to the tripod/shield/beam for upgrades.
Looking forward to the next one =)
Good marketing strategy activision!
I was considering getting back into COD and buying black ops on the weight of this game.
But I don't think I'll bother now.
Be nice if towers had an experience pool, that you could subtract from to upgrade any tower.
It'd stop one fully upgraded tower stealing kills and exp from other towers that need it more.