A while back I was extremely addicted to Urban Dead, which at that time was in a semi-beta stage and still receiving feature updates on a very regular basis. While simple, the simulation of survival in a zombie apocalypse (or being a terrible, flesh-eating zombie, depending) was very strong, arguably superior to any commercial game on the market. Unfortunately, eventually my zombies ran out of skills to take and my single living character decided to revert to huddling inside a heavily barricaded building as killing zombies had no real payoff and he'd run out of *productive* skills to take (there were still a few others, but they didn't fit his style.). I went back recently, as several new features had been added, but I'm running into the same problem: barricades dramatically tilted the balance of the game in favor of the survivors. Short of a coordinated effort by a large number of zombies, humans inside a sufficiently barricaded building (especially in large numbers) are in virtually no danger, as the zombie has to waste most of their day's actions (if not all of them) knocking through the barricade to get at them, leaving little or no time to feast on juicy human flesh. And in sufficient numbers, a barricade can be quickly reestablished before the zombie is joined by additional zed brethren, allowing the humans to beat down the interloper and dump them outside before they can reawaken. Since the zombies gain no experience for anything other than feasting on rich, juicy human, this makes starting new characters as zombies virtually impossible, and even hardened old zombies can go days without accomplishing a single damned thing. There are no free range humans anymore, so...whoops. No fun being a zombie.
I was, however, turned on to a newer browser game in a similar style: Nexus War. Nexus War is a significantly more polished effort with lots of interface niceties that Urban Dead lacks, a class tree system, morality, randomly generated descriptions, a fully designed map with other dimensions and such, and badges, among other things. My only issue with it so far is that the generic mortal skills that you're stuck with until level 10 aren't the most exciting things in the world. Oh, and Nexus War also generates action points significantly faster than Urban Dead, so you can viably play each character twice in a single 24-hour period, though you may or may not remember to or feel like doing so.
I was, however, turned on to a newer browser game in a similar style: Nexus War. Nexus War is a significantly more polished effort with lots of interface niceties that Urban Dead lacks, a class tree system, morality, randomly generated descriptions, a fully designed map with other dimensions and such, and badges, among other things. My only issue with it so far is that the generic mortal skills that you're stuck with until level 10 aren't the most exciting things in the world. Oh, and Nexus War also generates action points significantly faster than Urban Dead, so you can viably play each character twice in a single 24-hour period, though you may or may not remember to or feel like doing so.