Game Doctors’ ZombieSmash and ZombieSmash HD have already been highly rated and greatly enjoyed since their launch last year. Over that time, both apps have been upgraded with quite a bit more content and tweaks, including a secondary campaign. Coming next month, fans will be able to test their wits against living opponents in head-to-head multiplayer.

In an update scheduled to be available in the App Store this August, ZombieSmash fans will find that they have a new enemy to face. In what appears too good to be true, Joey unexpectedly comes across another survivor, Danny, after all this time. Indeed, the feeling of relief quickly fades as Danny appears to be suffering from an extreme case of paranoia due to the stress and fear of fending off hordes of the undead as well.

Unfortunately, this means Danny and Joey won’t be joining forces. Instead, the two begin to fight one another, sending additional zombies to the others’ home. Can you survive the standard zombie onslaught, plus your new foe’s offenses? Only time will tell as you attempt to unleash the proper dose of weaponry while taunting and playing mind tricks on one another using Game Center’s voice chat system.

ZombieSmash is designed for iPhone and iPod touch running iOS 3.1.3 or later, and available as a free download for the remainder of the day (07/21). ZombieSmash HD is compatible with iPad running iOS 3.2 or later, and available for just $.99 for the remainder of the day (07/21).