Space Invaders
PLAY !

  Left arrow - move left
  Right arrow - move right
 
  Space - Fire missile
 
 P - Pause/unpause game 
 Q - Quit game 

Japanese company Taito had the inspired idea around 1978 that killing aliens was extremely good fun. So they invented a game called Space Invaders, lots of history then followed, some people got rich and so on...

It's a simple game with simple graphics, but it has one of the most vital assets for any computer game gameplay. Modern games seem to forget this with their fancy "3D graphics" and "millions of dollars". All you need is a pointy green thing which shoots white stuff at a rampaging invasion of wobbling blobs. They don't make 'em like they used to.