Playing as Earth Command Trooper Aileen Harding, gamers will take on more than 100 different types of aliens and learn new abilities and skills as they progress. Aiding players in their cause are 20 different weapons, including quad-barreled lasers, nanobot swarms, and more conventional flamethrowers.Accompanying Aileen is an indestructible robot that serves as both an ally in battle and a vendor from which she can buy items. The robot can also upgrade existing weapons and can upgrade itself with new abilities.The PSP version will feature cooperative play for up to four players through the handheld's Wi-Fi capabilities.