7 Days to Die is one of the many "Early Access" zombie survival games that have been around for the past decade or so and are still under development. While this game might not be the most unique or polished game, I still manage to come back every now and then and have a blast with my friends, whether we play vanilla or via the "Darkness Falls" mod. It's easy to lose track of time playing this game, and there is alwasy something to do, even after getting most of your skills up. Usually by the time your almost done, the developers release a new update by then with some more things to do or explore. Recommend getting this game on a sale as it usually goes down to $5 or so on steam every now and then. Definitely better with friends btw, although I find the single player enjoyable as well.