Despite the name, Yet Another Zombie Defense is more a dual stick shooter than Tower Defense game. There might be a few elements, reminiscent of Tower Defense strategy, but success owes much to the player's ability to react quickly via the use of their thumbs.
Working on a wave basis, each in game night pits the player against an increasingly large, tougher and faster horde of zombies. At first, all that stands between the player and the zombies is their trusty pistol, but it's possible to upgrade such things. Frequently, the zombies drop money which can be used to either buy better weapons, more ammo, barricades or even an auto turret. Such tools are pretty useful at times, certainly when things get fraught.
The weapons available cover all the suitable zombie fighting tools, such as a shotgun, rocket launcher and flamethrower. Attach one of these to an auto turret and it can make all the difference between life and death. Similarly, create a form of maze with some wooden or steel barricades and it can slow the horde down enough to be able to take them out with little damage to oneself.
Problems lie in this format, though. Yet Another Zombie Defense is really quite simple with little expansion on the initial format. Worst of all, there's no multi tasking support meaning the player loses all their progress if they have to leave the app even for just a moment. Given the increasingly lengthy nature of the waves, it gets a bit frustrating repeating earlier stages over and over again, simply because a call or SMS has been received.
The potential is certainly here and it's great to see Yet Another Zombie Defense avoid an easy path towards in-app purchases to speed progress along, but it's more something to keep an eye on at the moment rather than lose hours of the day to.