Want to know how addictive UFC 2009 Undisputed is? Take a look at this:

　　That's my hand, a day after playing THQ's upcoming mixed martial arts game for an extended period of time. That disgusting pink spot in the middle of my palm is the blister I got from a result of that extended play session. Yes, I got a blister playing a videogame. I can't remember the last time that happened to me.

　　Why that blister appeared on the middle of my palm (and not, say, on my thumb) I'll get to in a bit. First, let me set the stage for you. Last week, we received the PS3 version of the upcoming downloadable demo for UFC 2009 Undisputed. The game, being published by THQ and developed by Yuke's, is the first licensed UFC game since 2004's mediocre UFC Sudden Impact. The demo, which will be available on PSN and XBL on April 23, features two modes: an extensive tutorial to get you used to the game's in-depth controls, and a single exhibition fight between Mauricio "Shogun" Rua and Chuck Liddell.

　　The Liddell/Rua exhibition--which will be a highlight of this weekend's UFC 97 in Montreal--proves to be a fantastic exhibition of UFC's gameplay and the different fighting styles found in the game. Liddell, a pure striker is as deadly as can be when standing up, capable of an awesome barrage of kicks and punches-- including that vicious overhead right hook--any one of which can take Rua out in a single shot. Rua, while no slouch in the kick department, is much more adept at clinching, mat work, and submission. Pit these two different styles of fighting, both equally dangerous, against one another and you've got a chess match in the UFC 2009 demo that speaks volumes about the strategic depth this game contains.

　　Over the past few days, I've played the demo over and over against both the CPU and against other folks in the office. The demo is passable in single player, though the AI lack of aggression and skill leaves something to be desired. And while I'm hoping the AI poses a stiffer challenge in the final version, Undisputed really comes to life when playing with a friend, preferably side by side on the same console, where the smack talk and the non-stop shouting can flow.

　　Undeniably, there is a lot to learn when you first pick up the UFC demo. The game's controls are deep yet have a logic and flow to them that unfolds the more you play it. Striking is simple--the four face buttons are tied to left and right punches and left and right kicks, with the L1 and L2 buttons modifying your strikes high and low, respectively.

　　For your first few fights, these controls will likely be all you need to end a fight, especially when playing with the hard-hitting Liddell. Much as in the real thing, fights can end quickly in Undisputed, with a punch or kick landing in just the right spot to send a guy crumpling to the mat, out cold. The fact that a lucky strike can end a fight acts as a pretty clever balancing act in the game; something to keep even expert players wary of their opponents, who might be able to end a fight with a single well-placed punch. Early on, you'll learn to defend early and often in Undisputed. The R2 and R1 buttons are for blocking low and high respectively, and you'll need to get your defense together if you hope to last more than one round in this game.

　　Stand-up fighting in Undisputed is a lot fun but I'd argue that the game really begins to come alive strategically once both fighters hit the ground. Depending on the position you find yourself in, you can still punch your opponent but there's also a ton of jockeying for position on the mat that ups the strategic jockeying in the game. There's mat-specific controls, and most are centered on the right analog stick. Essentially the idea on the ground is to continually improve your position on your opponent. To do so, you trace circles on the outside edge of the right analog stick. A successful motion (known as a transition) will mean you'll improve your position on your opponent. For example, when crouching above your opponent while your opponent is on his back, a successful transition might result in your fighter moving to half guard, side mount, or reverse mount. When a fighter is on his back, a successful transition means moving from guard to an escape or even to a submission (such as when catching the arm of your foe as he's punching and instantaneously transitioning to an arm lock submission). Defending against these transitions is also tied to movements on the right analog stick.

　　Submission attempts can happen at practically any time. To attempt a submission, you simply press the R3 button; if the attempt is successful, you'll transfer to a submission animation. The gameplay changes here dramatically--going from a cat and mouse game of careful feints into an all out frantic button masher. To submit an opponent (or defend against a submission attempt), you can either move the right stick around in rapid circles or press the face buttons like a madman.

　　It's those submission moves that did my right palm in. You see, it wasn't until later that I realized you could use the buttons to defend against submissions so, in my zeal to protect my fighter from a tapout, I palmed the top of the right analog stick and moved the stick around as fast as I could. It wasn't until an hour later that I realized that the motion was slowly eating away the skin of my palm, leaving a disgusting weeping wound in its place.

　　I spent the following weekend in pain and cursing the game's addictive nature, yet still not able to get it out of my head. I've played the game against other GameSpot editors since and it seems like no two fights have ended in the same way. From the time I accidentally leaned forward with Shogun Rua just as Shaun McInnis was throwing a vicious Chuck Liddell kick into his face, to the time I actually managed to make Homer Rabara's Shogun tap out while playing as Liddell, every fight in UFC Undisputed will have a storyline all its own. Considering the demo features just two fighters from the game's 80-plus-strong roster--each with his own combination of strength, stamina, and style--it seems like Undisputed's dead-serious focus on MMA styles and realism is paying gameplay dividends.

　　I can't wait to get my hands on the rest of the roster once the game is released on May 19 to see how the different fighters play. The game's single player experience will have a career mode but, as with other fighting games, Undisputed's best chance at longevity is in making sure the online play is flawless and lag-free. The game's subtle and engaging fighting engine deserves that kind of extra special online attention.

　　One tip for THQ: You might want to consider packing in some sort of palm protectors once the game is released on May 19. FYI, I've heard UFC has some nice gloves available…