Tiny Zomby: The Barricade
A bomb goes off, the radiation does the rest, and the whole town wants a piece of you. You play a kid on a watchtower with a rifle, a wooden fence, and little else. Drag to aim, tap to shoot, and keep the barricade standing.
Collect the coins the zombies drop and use them to plant mines where they walk. You can also save up for a shotgun. The game has six stages, with six waves in each stage and a boss at the end of each stage. The airport is where it gets nasty.