A
computer /
video game where
points are scored or progress is made by
shooting
projectiles at enemies. This is about the only common element
between most shoot 'em ups, as the entity you control, and the style in
which the world is navigated vary widely.
When the term is used on it's own by the gaming press or most gamers,
it usually refers to games where you control a space ship, and where the
screen scrolls either horizontally (eg, Gradius, R-Type), or vertically
(eg, Gunhed, Xevious, Aleste, 1942), and also top down shoot 'em ups (eg,
Ikari Warriors, Mercs), where you control a character viewed from above
who can shoot and move freely in eight directions.
In recent years, the first person shoot 'em up (FPS) has become
prevalant, and the traditional shoot 'em up has fallen to the wayside,
only really retaining popularity in Japan and in the arcades. FPS games
are viewed through the eyes of the character, and (usually) full freedom
of movement is given. When the phrase "shoot 'em up" is used in the
mainstream press, it more often than not refers to FPS games, unless it is
in the context of classic gaming.
There is debate as to whether platform shoot 'em ups (eg, Metal Slug,
Gunstar Heroes, Contra, Assault Suits Valken) should be filed under
platformer or shoot 'em up, being simplistic platformers with a heavy
emphasis on shooting stuff. The truth is that they fit comfortably into
both genres.
There are also many examples of shoot ‘em ups that don’t fit into the styles described above yet still fit the defining criterea. Though the one exception is light gun games, which are generally given their own category.
See also: shmups