Don't let their cold, clammy skin fool you - zombies are hot right now. So hot, in fact, they're making a tower defence comeback in Zombie Attack! Second Wave.

Offering much needed structural changes and new controls, IUGO's sequel promises to breathe new life into this undead take on tower defence.

As the lone survivor of a zombie apocalypse, the game charges you with staying alive by building defensive turrets to kill any undead aggressors. Levels are free-range with zombies able to saunter about at will, instead of being restricted to a specific path.

Of course, this means you're at liberty to build defences anywhere within a level as well in order to prevent zombies from destroying your mobile safe house.

Doing so means moving your survivor, via a virtual directional pad, and tapping out build commands from a vertical menu along the right side of the screen.

There's an alternative tilt control scheme brought over from the first game, though the default touch configuration is better. Granted, the new touch controls aren't perfect - we'd be curious to see a tap-to-move option added to complement the directional pad - but it's a dramatic improvement from the first game.

You've got a varied arsenal at your fingertips from all-purpose rifles, splash damage cannons, and burning flamethrower.

Along with these typical defences, there are a few inventive additions that support the free-roaming style of play. The rotating choppa, for instance, doesn't fire any projectiles; instead, any zombies within range are cut up by its spinning blades.

Decoy turrets are the most innovative of the bunch, fooling zombies with a mannequin, then dealing damage when they move into range. When the decoy takes enough damage, it explodes and hurts nearby enemies in the process. Upgrades to the decoy and other turrets with cash collected from dead undead boosts range and power too.

Six zombie varieties attack at four locations: ruined bridge, graveyard, trailer park, and backyard.

Survival mode has you racking up high scores on each stage against a never-ending onslaught of enemies. There are also Challenges that put restrictions on what turrets you can build and the types of zombies that appear.

Special situations highlight environmental factors like crumbling concrete in the ruined bridge level. These feature endless waves like in Survival mode, though we'd prefer if the number of waves were capped.

Leaderboards for Survival mode should provide reason to come back and aim for a top score and more than a dozen Challenges ought to keep you busy.

Although it would be great to see a more formal career mode or campaign, Zombie Attack! Second Wave looks to get the fundamentals right and that's enough to deserve a second look come its release to the App Store within the next couple weeks.