If you've never had an out-of-body experience before, you could always try Geist, a first-person-perspective action adventure exclusively for the GameCube. In the game, your character's spirit is ripped from his body, leaving you to explore a high-tech, heavily guarded compound as an invisible being capable of possessing other living creatures--and even certain objects. This unique premise sets up some unusual situations and some cleverly designed puzzles as you infiltrate your enemies' ranks by borrowing their bodies and walking among them. Since much of your time is spent occupying the personal space of armed guards, though, much of the game plays out like a standard first-person shooter. The game's ghostly twist is also central to its multiplayer mode, which can be played with or without computer-controlled opponents and teammates. Geist's graphics and sound aren't that remarkable by current standards, and despite its long time spent in development, it's got some obvious rough edges. So its finer points aren't right there on the surface. And maybe that's befitting a game about an invisible man.

You get to be the star of this particular ghost story.

The man in question is John Raimi, a scientist called in with a special forces unit to declaw the Volks Corporation, located somewhere in France. Much like Half-Life's Black Mesa research facility, Volks is a high-tech subterranean laboratory in which dangerous, barely controllable top secret experiments are taking place. In short, Volks is up to no good, so Raimi and company storm in to get their hands on incriminating evidence. But the ambush doesn't go according to plan. Soon Raimi finds himself separated from his squad, becoming the next subject of Volks' nefarious agenda. He's turned into this disembodied, energy-based life-form...and, by some chance, he's then able to escape the elaborate containment system designed to prevent him from running amok. Now it's payback time, and Raimi can see to it that his enemies don't even know what hit them.

It's a good thing there's more to Geist than first-person shooting. In the first few minutes of the game, a shoot-out erupts, and Raimi runs around blasting foes with a handgun while they whittle away at his health bar with their automatic rifles. Your enemies crumple like rag dolls when killed, and don't do much to try to avoid getting shot, so they don't make for particularly challenging opponents. The game's controls are a little sluggish, and the frame rate tends to noticeably bog down during battles, so Geist's first big action sequence falls flat. Fortunately, it's not long before you're transformed into a ghost, and the game gets considerably more interesting from there. Geist's single-player adventure is fairly short and should take you maybe 10 hours or fewer to complete, but it's got a good amount of variety. There's quite a bit of shooting, including more than a few battles against thick-skinned boss opponents. The nature of the action changes considerably depending on the host you possess and whatever weapon he or she happens to be carrying. You'll also get to possess everything from animals to conventional appliances while finding your way around Volks Corp. and uncovering the intentions of its eccentric leader.

As a ghost, you might expect you'd have free reign to wander the halls of Volks however you please. However, your new "body" has certain limitations. You can't pass through solid walls unless there's a noticeable gap in them allowing you to slip through. Volks has also set up certain defenses, preventing you from floating around unhindered. To make matters worse, your health constantly dwindles away and can only be restored by possessing a host or drawing energy from plants you'll find here and there. In practice, there's little danger in running out of health when in ghost form, but your limited life force puts a little pressure on you to keep moving forward. Occasionally you might get stumped by a puzzle and find yourself searching for where you need to go next. But between the game's linear structure and your access to a 3D map of your surroundings, it shouldn't be long before you figure out your next move.

First things first: Before you can possess human subjects, you may need to freak them out by tampering with their trusty appliances.

Geist's linear design helps ensure that the action remains reasonably well-paced, though it also makes a lot of the game's puzzles really simple. It's great that the game lets you possess both living creates and inanimate objects. However, you'll soon learn that pretty much the only inanimate objects the game lets you inhabit are the ones that help you get past an environmental obstacle of some sort. So you won't need to think much about why you're possessing that pile of dishes or that fuse--you'll do it because you can. One of the game's conceits is that, before possessing a living host, you must first weaken its mental defenses by scaring the living daylights out it. You'll do this by possessing computers, ladders, telephones, and more. The results of these freak-out sequences are sometimes creepy and sometimes amusing, but they're completely scripted. You'll wonder how the game might have been different if it gave you more freedom to accomplish your objectives rather than put you in a string of contrived situations, each with very specific solutions.