Shooter games are a subgenre of action game, which often test the player's speed and reaction time. It includes many subgenres that have the commonality of focusing on the actions of the avatar using some sort of weapons. Usually this weapon is a gun, try to get or some other long-range weapon. A common resource found in many shooter games is ammunition. Most commonly, the purpose of a shooter game is to shoot opponents and proceed through missions without the player character being killed or dying. A shooting game is a genre of video game where the player has limited spatial control of his or her character, and the focus is almost entirely on the defeat of the character's enemies using long-range weaponry.
Shoot 'em ups are a specific subgenre of shooters wherein the player may move up and down and left and right around the screen, typically firing straight forward.
Shoot 'em ups share common gameplay, but are often categorized by viewpoint. This includes fixed shooters on fixed screens, such as Space Invaders and Galaxian; scrolling shooters that mainly scroll in a single direction, such as Xevious and Darius; top-down shooters (sometimes referred to as twin-stick shooters) where the levels are controlled from an overhead viewpoint, such as Bosconian and Time Pilot; rail shooters where player movement is automatically guided down a fixed forward-scrolling "rail", such as Buck Rogers: Planet of Zoom and Space Harrier; and isometric shooters which use an isometric perspective, such as Zaxxon and Viewpoint. This genre also includes "run and gun" games which emphasize greater maneuvering or even jumping, such as Thexder, Contra and Metal Slug.