A new sale is sweeping the App Store in light of the release of Zombie Gunship [$.99]. Creator Limbic Software is offering its Tower Madness games for $0 in celebration of this lightest morsel of awesomeness. This is a sale with a total of two middling-to-good titles that should keep you pre-occupied if Gunship isn't in your wheelhouse. If it is, well, I suppose that's icing on the cake.

Here's the quick hit sales list:

• Tower Madness � $2.99 -> Free
• Tower Madness HD � $7.99 -> Free

We checked out Zombie Gunship earlier at WWDC 2011 in San Francisco. It's basically an AC-130 game that has you defending key objectives from an endless zombie horde. If you're familiar with any recent Call of Duty titles, you'll probably appreciate the AC-130 action part of the title more than flight enthusiasts. It has a similar look and feel to those mini-game sections in Activision's uber-popular war franchise.

More is coming to Zombie Gunship, by the way. At GDC, we were told that more zombie types, more weapons, and even more locations are coming in a free update. Neat!