The game is a horizontal scrolling shooter in which you take control of a jetpack propelled space warrior who travels between Parallel universes and worm holes (hence 4-D, or 4 dimensions) throughout the game. By flying over the top of the play field, you end up in an alternate universe. You travel back and forth defeating enemies until you reach a boss creature. On some occasions a worm hole will appear in the middle of the play field and you are taken to even stranger worlds...
The game contains at least six distinct worlds. You begin in a red zone populated by a variety of surreal enemies. The red zone also contains at least three kinds of powerups in the form of crystals. By going over the top of the red zone, you can enter a blue zone.
The blue zone is where the level boss first appears. Once the boss is sufficiently damaged, it will retreat to the red zone, where you can destroy it and advance to the next level. When the boss is not present, the level contains a selection of enemies that behave similarly to those in the red zone, although their appearance is somewhat different. By going over the top of the blue zone, you can return to the red zone.
Several randomly occurring phenomena in the red zone can take you to other worlds:
- A hole opens up and two green diamond-shaped objects emerge. If they catch you, you will be transported to a world with a blue sky and clouds, where you need to shoot a moving blue circle and avoid bullets from two giant eyeballs on the ground.
- A creature appears from the bottom of the screen and swallows you. You then traverse its vertically-scrolling digestive tract.
- Two bouncing mirrors appear from behind you and sweep across the screen. If they catch you, you will be transported to one of at least two possible locations:
- A field of orange spheres populated by blue pyramids.
- A cyan-colored hallway filled with giant stone heads, giant chalices, and a variety of floating masks.