Though the Japanese developer SNK closed its doors last fall, it is survived by two games for its long-lived NeoGeo arcade hardware: The King of Fighters 2001, which is currently available in arcades, and Metal Slug 4, which is being worked on by Korean developer Mega Enterprises. The Metal Slug series is considered by many to be among the last great side-scrolling action series, and it has seen the release of four games so far: Metal Slug, Metal Slug 2, Metal Slug X, and Metal Slug 3. Each of the games is famous for its fluid hand-drawn animations, comic characters, and intense firefights. In the series, players assume the role of a single soldier who can rescue POWs to recover powerful personal weapons and pilot a variety of different vehicles in the fight against an evil army of soldiers and an alien invasion.