It's good, but limited...
I got to say, it's one hell of a nice zombie defense game(there are a few too many nowadays though).
The choice of weapons is huge which is nice, the powerups are handy too.
But the bunker should have lots & lots more upgrades and such(also visual so you actually see that it's being fortified), and were are the melee weapons - a chainsaw would be nice =) -.
Graphics are stunning, sound is nice & creepy, bunker options should've been way more expanded, having such a bunker vs. such a large mass of zombies isn't right.
Overall, good game =)