Robots Vs. Zombies is a fairly dull slightly modified tower defense game.
The point of interest is that you control a mobile robot that can shoot the creeps (in this case obviously zombies). This robot is essentially similar to the tank from Tank Destroyer in terms of how you control it-i.e. nice, smooth and easy controls.
Obviously, you can also build turrets. There's not much variety, though. The upgrade tree has basically no interesting features that I can tell.
If an enemy reaches the goal area, it picks up one of your MacGuffins (sadly not brains) and tries to carry it back to the gate. If it dies before it gets there, it drops it in place, meaning the next zombie to get that far can get it sooner. It's a kind of interesting, but also very annoying, mechanic in my mind.
Why are you shut in this nearly indefensible room trying to hold off zombies, and why don't you just shut the danged door? Who knows?
A fairly boring and somewhat inferior tower defense game, although it's got pretty nice graphics. Unless you're looking to see huge puddles of blood on the floor where the zombies buy it, you're better off playing a more interesting tower defense game than this one.