Halo: Combat Evolved is a first-person shooter video game. It starts the game series called "Halo". It came out in 2001 for Xbox and was released on the personal computer later. It became very popular and has made a lot of money. Many people say it is the Xbox's "killer app", which means the best program for a system. Because it was liked by so many people, there have even been 6 books and a Graphic Novel written about it. Halo is rated M for mature.