Most of the best zombie games feature level ups, new weapons, and nightly waves of zombies to attack. Dead of Night is the same style of game, although it focuses much more on strategy and base building then just having the most powerful weapons. In Dead of Night, you must fortify your base with strong walls and traps - and you've got a medic and a scientist to protect so that they can help you win.
The zombies come in very large waves and amusingly burst into flames every morning, so as long as your base allows you to survive the night you'll stay alive even if you don't kill every zombie. Post your best scores and how many nights you survived!