Nothing amazing, but guaranteed to amuse you for hours on end.
Worms 4: Mayhem pits you and your wriggly invertebrate team against either a human player or the computer. Your arsenal ranges from the simple shotgun to bizarre weapons like explosive cows and a concrete donkey, and is fired off in turns. Worms works like a fancy game of chess - you move one of your Worms towards the other team (or alternatively stay back and aim your weapon) and fire, and your turn is over. Of course, you have a time limit to do this in. Worms 4 comes with a bounty of maps tucked under it's belt, with loads more unlockable. Improving on it's predecessors, your invertebrates are fully customizable, and so are there weapons. With enough imagination, you can really get some wacky characters. My team turned out to be a group of medieval pimp worms.
Worms 4 is devishly difficult to grasp a hold of, and manoeuvring your wiggler (don't think about that twice) is frustratingly hard at first, but after a good hour you'll have mastered the controls like a pilot. A good pilot, that is. Worms 4 has a tendency to move the camera around to awkward angles, which can really tick you off. Aiming your weapon is fairly simple, just hold down Q and fire.
The graphics in Worms 4 are frankly very lackluster - you can see what the developer was aiming for, but it just turned out undercooked. Destructible environments are somewhat pathetic as you'll be left with various floating structures and bricks just looking ugly. Crappy lighting means that shadows can take seconds to actually even show up. Saving the graphics from total failure is the animation - Worms and explosions and all assorted other aspects animate fluidly in a very charming way.
The sound in Worms 4 is great, but you'll start to tire from the repetive lines that your team repeats, as there seems to be about 10 for a certain event. There's hardly any variety between the music, but it's all quite good.
Overall, Worms 4 is a solid game with nothing spectacular to offer, but amusing none-the-less. If you're a fan of turn-based strategy or the previous Worms games, then you'll thoroughly enjoy Worms 4. If not, then you won't get much out of this game.