Space Invaders / GAME HISTORY

Why Do Space Invaders’ Aliens Speed Up as You Shoot Them?

The shrinking formation changes the drawing workload; it does not make the processor run at a faster clock.

By Patchlo Editorial Desk · Published October 22, 2026 · Sources checked October 22, 2026

Scope: Tomohiro Nishikado’s account of the 1978 arcade version. Later ports can implement pacing differently.

Less to draw, less time to wait

The machine’s clock does not speed up. The shortened drawing cycle gets back to each survivor sooner. Nishikado kept the effect because it made the fight more interesting.

The design was already about clearing the screen

In a separate interview, Nishikado described liking two things about Breakout: having to clear every block before advancing, and the increasing difficulty of hitting the last one. He wanted to carry that kind of pressure into a shooting game.

That helps explain why an awkward hardware limit could be useful. The screen looks safer as enemies disappear, but finishing the wave asks more of the player.

Does the same explanation apply to every port?

No. A later version can reproduce the rising pressure with a deliberate speed rule. Seeing fewer aliens move faster does not prove that a later machine is reaching the same limit. The effect and the implementation are separate questions.

That is also why a Mario trick working in one release does not settle what happens in another.