drums, and vocals, while a total of eight players can compete in a Battle of the Bands. The Xbox 360, PlayStation 3, and Wii versions of the games support multiplayer modes over their respective network services. The four difficulty levels for each song afford the player a learning curve in order to help him/her progress in skill. The first difficulty level, Easy, only focuses on the first three fret buttons while displaying a significantly reduced number of notes for the player to play. Medium introduces the fourth (blue) fret button, and Hard includes the final fret button while adding additional notes. The addition of the orange fret button forces players to move their fingers up and down the neck. Expert does not introduce any other frets to learn, but adds more notes in a manner designed to challenge the player and to simulate the player's hands to move in a sequence similar to a real guitar. A difficulty added in World Tour is Beginner, which only requires the player to strum to the basic rhythm; holding the fret buttons becomes unnecessary. Another new difficulty only for drums was added to Metallica known as Expert+, which uses the double bass pedal. Guitar Hero: Warriors of Rock is the sixth installment in the franchise and introduced a new take on the Career mode of previous games. Rather than being a quest for fame and glory with the band travelling through different venues, Warriors of Rock features the "Quest Mode" as the primary campaign mode. Quest Mode tells the story of an ancient warrior who was defeated by a powerful monster and his mystical guitar was lost. The player must amass a team of rockers to help recover this guitar and defeat the monster (called "The Beast"). As the player progresses through the mode, the rockers joining them will transform based on the number of stars earned from songs played. These transformations will empower the player with extra abilities in a song such as constant score multipliers or Star Power bonuses. These abilities are each unique to the individual rockers and by using them effectively, it is possible now to earn up to forty stars for a single song. Characters and customization When playing through Career mode or in other parts of the Guitar Hero games, the player has the option to select one of several pre-created avatar characters, who will be shown