This review is from the perspective of one who has not played a previous game in the Worms franchise.
Worms, a simple concept- Groups of worms fight to the death in enviornments ranging from simple to complex, littered with explosive barrels, guns, toxic gas, testing tubes with eyeballs inside, and many other borderline ridiculous items.
Rather simple, yes? Now add some nice physics to it, and add some items, for example perhaps..Bazookas, grenades, dynamite, flamethrowers, sentry guns, water pistols, air strikes, as well as your own grandmother. That last one is a stinker.
Imagine a worm gracefully flying through the air after getting hit by dynamite, followed by said worm landing on a landmine, flying into a small pit with a sentry gun and being shot into the air moments after. Seconds later, the worm has fallen into the water and met his demise. How unfortunate.
Unlikely, yes? Mostly, but not entirely. Now imagine hitting worms off of an edge with a baseball bat, or simply prodding the worm the minimum distance to make him fall to his death, an insult to injury. Throwing an angry buffalo at a group of worms as it literally explodes them 6 feet into the ground. Throwing the holy hand grenade to launch a worm into the sky, dropping dynamite from your jetpack as you fly away from your helpless foes, poisioning multiple worms from a distance to cause damage over time, and even beginning the event that put an end to the dinosaurs. Meteors, explosions, the map becomes swiss cheese. Many casualties ensue-if not becoming a mass-homocide-suicide mix that turns into a draw.
Only one problem, chances are that you're only going to experience this sweet action if you've got some buddies to play the game with, so you're going to have to convince your friends to buy the game if they don't have it already. The single player in this game isn't bad but it can be rather unfair and overall is only for unlocking additional worms, which isn't 100% neccessary.
So forget about the single player and just focus on the multiplayer. Get some friends and cause some explosions, because this game is a lot of fun.