"Earth is being invaded and you’re our last hope! An alien race threatens to conquer the only inhabited planet in our solar system. You will be at the helm of our last line of defense, an arsenal created many years ago in order to contain an invisible threat that most thought would never come to pass.
Keep the alien spacecraft from abducting the last surviving citizens of Earth, destroy the aliens, and save the planet.
This arcade game blends the gameplay of Tower Defense with the classic Space Invaders and will provide you with hours of endless fun.
High-definition graphics for iPhone 4 iPad 2
25 incredible levels that will take you all around the world
More than 20 different weapons
Over 40 different weapon upgrades
More than 20 different enemy types
Excellent soundtrack and sound effects
Set of achievements all compatible with Game Center"
Source: The Developer Website.