The iPhone or iPod Touch is certainly the device to own if you're into defending things. Whether you like defending using towers, flicking, or in the case of MonsterKill [App Store], gesture-based spell casting, the App Store has you covered.
The goal of the game is to defend your wall from an onslaught from zombies, wolf men, vampires, and frankenstein monsters, each with slightly different behaviors. Slaying these monsters involves casting spells. The simplest attack is executed by just swiping across enemies to cut them in half. The first spell you come across is a lightning bolt, and to cast it you just draw a lightning bolt on screen. Other spells include an ice block, cast by drawing a V and a fireball cast by drawing an upward arrow.
The gesture system actually works pretty well, and seems to be a cool way to handle multiple attacks without any kind of action bar to select them. It can be kind of hard to aim your spells, but after playing the game for a bit you get a hang of where you need to draw the various gestures to get their effects to end up where you want them.
The trailer by Origin8 shows the gestures and gameplay:
The meter at the top of the screen shows how much more mana you have to cast spells, and it slowly regenerates over time. Between levels, you will have the opportunity to upgrade your spells and repair your wall like most similar games.
If you haven't had fun playing castle defenders in the past, the gesture system likely isn't enough to make you like MonsterKill. Like most Castle Defense games, it can get a bit monotonous grinding through wave after wave of attackers in order to buy upgrades. But, clearly the genre has a big following, and if you're a fan, Monsterkill is certainly worth considering.
App Store Link: MonsterKill, 99¢