Worms 4: Mayhem is a 3D artillery game in the Worms series developed by Team17. It is much like its 3D predecessor Worms 3D, except that players can customize their worm's appearance (hats/helmets, glasses, facial hair, gloves/hands) as well as create their own unique weapons in an added feature called "The Weapon Factory." The game also contains a shop where users can buy various items, using points won by completing story missions, activities or unlocking trophies. Shop items include new maps, new accessories and attire, personality banks (voices) and game styles. There are several new weapons included in the new game such as Bubble Trouble, Icarus Potion, Poison Arrow, Sniper Rifle, Inflatable Scouser, Tail Nail and Starburst (Which, in fact, only replaces the Kamikaze).
Worms 4: Mayhem has a lot more in-depth story mode than the previous games. Instead of just completing missions with some minor background story told, proper introductory cut-scenes reveal information about the mission's background. The story actually begins in the tutorials, in which the player's own team of worms arrives to the Worminkle University. There they meet Professor Worminkle (who resembles Albert Einstein and Doc Brown), who trains the player and teaches the methods of using various weapons. In Story Mode, Worminkle sends the player to destroy the enemies buildings and sneak into their construction sites. After the fifth mission, Worminkle and the player travel back in time to the Middles Ages using the Professor's time machine. Worminkle's time machine becomes damaged and they are then attacked by wizards and knights. After fixing the time machine, the missions continue in the Wild West. The Professor's time machine runs on gold, which they need more of if they want to get forward. So they need to also fight against the fearsome Boggy the Kid. After getting the gold, the player's quest continues to the Ancient Arabia, which is being conquered by Ali Baboon and his pesky thieves. Ali Baboon has stolen the Queen's jewels, and the player's mission is to stop him. After completing their mission in Arabia, Worminkle makes a few fixes with his time machine, but accidentally drops a letter, which is read by the player's team of worms. It is said in the letter, that the Government is planning to build a new research laboratory, replacing Worminkle University. Worminkle quickly takes the letter back, and continues the journey with the player. After they stop in the Prehistoric times, Worminkle then tells the player that he only used the player to stop the Government's plans. He then betrays them, and leaves, but fortunately crashes into a mountain, giving enough time for the player to catch him. After battling with many caveworms, the player gets to the Professor, takes the time machine, and flies away, leaving Professor Worminkle to the history.