Philips Magnavox Videogames and the Entertainment Revolution Trigger Happy - Manual (Page 207)

Trigger Happy
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dispensation of characters, in order to uncover more
text than is currently viewable on the open section. We
are now all familiar with the process of smoothly
scrolling down a word-processing document or Web
page: videogames got there first.
Early scrolling games were mostly of the vertical
shoot-’em-up genre. Rather than sit waiting for aliens
to come knocking at one’s defenses, as in Space
Invaders (1978), the player was in constant motion,
rushing forever upward on a long, linear strip of space,
dodging and fighting enemies along the way. But most
revolutionary was a type of space delineated by the
combination of horizontal scrolling with a variation on
the wraparound concept.
This idea in fact featured in one of the earliest
scrolling games, Defender (1980 [see fig. 9]), for many
reasons a classic of radical design, in which the player’s
ship is free to fly left or right, or simply to hover,
spitting lasers at the evil hordes. When the ship is in
motion, it remains in the center of the screen;
everything else scrolls by to give the illusion of
movement. But fly far enough in one direction and the
player approaches the original starting point, from the
opposite direction. Horizontally, then, the play area is
finite but unbounded.