Invaders 1978 is a very close approximation of the original Space Invaders game, down to there being no high score save or even a pause feature. The only very few minor differences include either the top invader “winking” or Invaders' explosions not being centered when shot (depending on monitor used), the number of lives remaining are displayed at the top right, rather than at the bottom of the screen, and the UFO comes out at intervals that are a little longer than with the original.
Also, on the 02 version, the Invaders are more aggressive, dropping faster bombs at times, and the UFO will stop coming out when there are nine invaders. In the original arcade version, it would still come out if there were nine, but not if there were any less.
- Bottom invaders–10 points
- Middle invaders–20 points
- Top invaders–30 points
- UFO–50, 100, 150, or 300 points
- Extra laser base–1000 points
- Start game–any key
- Move laser cannon–left ctrl and alt key (left and right), right ctrl key (right)
- Fire–right shift key
- Exit/quit game–escape key