You've been warned (I guess)

The first perspective given was to present the illusion of a generic space invaders game. The second, which is a side view, was meant to expose what appeared to be an initial flaw in the game, that is, the fact that no bullets seemed to actually collide. It is revealed that you're space ship is actually firing at empty air far away from the actual invasion force. In addition, the invasion force curiously seems to spell PEACE when looked at this angle. The idea was to give some sort of personality to the alien forces while making you question what you're player character is actually going.

The 3rd overhead view is meant to show that the whole thing is really just another electronic system, while the 4th is meant to break all immersion and show the whole thing is set up inside an elaborate game space.