Philips Magnavox Videogames and the Entertainment Revolution Trigger Happy - Manual (Page 212)

Trigger Happy
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vertically or horizontally, but diagonally up and to the
right. “Isometric” means “constant measurements.” In
architectural parlance, “isometric projection” is the
name given to a type of drawing in which all horizontal
lines are drawn at an angle of thirty degrees to the
horizontal plane of projection. In other words, parallel
lines do not converge, and equal emphasis is given to
all three planes. In videogame terms, this means that an
illusion of solidity is created while preserving an
external viewpoint. You could see three sides of an
object rather than just one. And now, crucially, the
game screen was not just a neutral arena; it had become
an environment.
By means of simple jagged lines, Defender had
created an illusion of planetary surface by sketching a
mountain range; below the level of the mountains it
was safe to drop off rescued humans. But the
mountains worked only to delimit functional areas of
the arena in this way; they were otherwise
metaphorically “behind” the player and did not have to
be negotiated. Later derivatives of the scrolling 2D
shoot-’em-up, such as Scramble, did require the
navigation of tortuous tunnels, but this design only in
effect limited the play area, which remained as fluid
and empty as ever. The player’s ship in Zaxxon,