The game itself is not bad. The intro was a bit short and you just get told to mindlessly blast zombies outside your base, but that was no big deal.
The game itself was fast-paced, which I enjoyed, but the game was horrendously short, with only 10 rounds, which I think could've been extended if the difficulty ramp wasn't so steep. You see, after level 6 when you get the Minigun, you're basically relying on firing it into the crowd of zombies chasing you and pressing C for an airstrike, so the game turns into you running and trying to get enough kills to keep the airstrikes coming before you run out of ammo. I didn't like how all of the other guns became completely useless after level 6 because there were just so many zombies.
Another peeve of mine was that you couldn't choose your weapons and were stuck with the, "best one". That's not a very good way to handle it. It's nice to have the best weapon auto-equipped, but I found myself liking the Shotgun over the Barrettas (those dual pistol things), but I couldn't switch back because of the weapon system.
If you make another game like this in the future, I would recommend putting in an upgrade system for your weapons, more rounds, and a larger playing field. It got cramped very quickly when the zombies starting coming in by the dozens. Also, when I used the Minigun, I had horrendous lag whenever I tried to move and fire. I don't know if it was my computer's fault or if the animation was just too much, but if there is a way that you could fix that, maybe with just a simple quality button (which I couldn't find), the game would be even better.
Overall, the game was fun, fast-paced, but short. This game is good, but it can be better.