Mutant Nightmare continues the beat-'em-up action that the series has become known for. Like the previous game, up to four people can play at once, each controlling one of the color-coded heroes (well, they're all green, but their masks are different colors). Besides the fun of playing multiplayer, there are also extra benefits. By fighting alongside your buddies, you can pull off cooperative attacks and the extra powerful "Hyper Combos."
The biggest new addition to this sequel's gameplay is the Ultimate Turtle Form. As you progress through the game, you earn ninja scrolls, which eventually grant you new powers. With these new skills comes a new appearance. The turtles gain new outfits and their trademark weapons before bigger and more powerful-looking. The ability to evolve the characters this time around could add some depth to the gameplay that was missing in the previous entries in the series.
Old school Turtles fans will appreciate Mutant Nightmare's unlockable bonus, the 1991 arcade hit, Teenage Mutant Ninja Turtles: Turtles in Time. This was the sequel to the original TMNT arcade game, which was featured as a hidden extra in this game's predecessor. Like the main game, this brawler supports up to four players at once, but it stars all the character from the original cartoon series. Unfortunately, like the previous port of the first arcade game, Konami was unable to get the rights to use all of the original music and sound effects (due to mildly complicated licensing reasons), so many sounds have been replaced or eliminated. It's a shame, but some Turtles in Time is better than none at all.
If you've played any of the other two recent Turtles adventures, you know exactly what to expect from Mutant Nightmare. Hopefully the upgrade system will add an extra level to the overall package, since the simplicity of the previous games were one of their main drawbacks.