Trigger Happy

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,

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Magnavox Videogames and the Entertainment Revolution Trigger Happy manual