A real tribute to Flash's potential.
This game wins in just about every category. It's challenging without being impossible, it's fun for a little quick zombie slaughter, but has replay value in that it's just fun to see how many times in a row you can survive all 20 days. It challenges both your mind and your reflexes, forcing you to manage your precious few daylight hours in order to survive, while testing your reflexes as you attempt to score as many headshots as possible before your clip runs out.
That said, this game does tend to rely on random chance a little too much, and the system for having survivors die during daylight searches is pretty lame. There were a couple times I lost the game, simply because the system would not allow me to keep my survivors, thus hindering my repair and weapon search efforts so substantially that defeat was inevitable. I would find a survivor while searching, and have him die during that very same search, resulting in a pointless waste of hours I could have spent repairing the barricade. Other times the game would report that survivors died during a search, when I was the only one and none were even found.
Even with its annoyances and bugs, most of the time this game plays just fine. It's definitely one of the best on the web.