You start the game by choosing your original body. You are a floating spirit (think "Casper") and you move the joystick over one of the four characters and push the button. Then, you invade that body and take over. You can even kill the others standing around you right then, or just venture off to battle the forces of evil (you are trying to rescue your girl).
You have two buttons, fire and jump. In addition, the fire button also acts as the button to possess a new body. So, if you are killed, your apparition floats out and you have to use the joystick to guide it to the enemy of choice and push the button to possess them. The complication here is that the game is over if you are killed and your apparition does not invade another body in time. This can happen in two ways: either you don't navigate to a nearby enemy soon enough (there is a time limit to possess) or, there is no enemy on the screen for you to invade. Bosses and some mini-bosses can not be possessed and in many scenes while you are running around, there are simply no enemies nearby.The game is more of a platform game than many of the previous GOTD platformers I have reviewed in that there is lots of running, jumping, elevators, platforms and other physical obstacles to conquer. Machines that shoot at you, enemies of a gigantic variety and some complicated routes keep you on your toes and all over the screen.
As you go, the goal (other than stay alive) is to collect keys that will eventually open doors to find your squeeze.
The main fun and hook of the game is in taking over lots of other bodies. The programmers did a good job in the variety of ways they behave. Some shoot guns, some punch and kick, some shoot lightning, some throw grenades and they all jump, crouch and run in different ways. A lot of the fun the game is invading a new creature and learning what his/her skills and weapons are.
The graphics are good, the game is fun and the spirit invasion makes it somewhat unique - it all adds up to a nice platformer.
NOTE/Addition: Per the comment from Rando below, I wanted to point out one other fact of the game. You can philosophically be reincarnated indefinitely, EXCEPT you have a "spirit energy" bar at the top of the screen. Each reincarnation takes some spirit energy and if you die (even with enemies around) and have no spirit energy left you are dead and can no longer reincarnate. Luckily, there are many items to grab hanging around that give you additional spirit energy. And, thus, played correctly, there is theoretically no limit to the repossessions.