This game is cool.  But you need an expantion pack to play the missions.  You need a memory card to play the Challenges and save.  This game is a tiny bit like 007 Goldeneye.  But it's Story Line is very different.  At first,you're killing bad humans.  But later in the game you kill Bad Aliens and help good Aliens.  It has two levels from 007 that you can unlock in the Challenges, but the actual story line is about Aliens.  The good thing about this game is that you can beat the missions with other people.  You can't do this on 007 Golden Eye.  This is a cool game and if you don't have it then you should get it.