Girls' Generation had a banner year in 2013: beginning with the release of I Got a Boy, one of their most successful albums yet, and ending with their win for Best Music Video at the inaugural YouTube Music Awards, the nine-piece group spent the year reaffirming their global stardom. They shore up these strengths on Mr.Mr., a set of songs that offers something for every kind of Girls' Generation and expands their musical reach. The title track, which was produced by Underdogs -- who have also worked with Britney Spears, Beyoncé, and Justin Timberlake -- is the best example of this, mixing a hip-hop beat and EDM-inspired buildups and drops into a Top 40-friendly concoction. Elsewhere, the group dabbles in retro sounds on the fittingly named "Europa," which nods to late-'80s Europop, and returns to a more traditional K-pop sound on the standout track "Goodbye." The ballad "Back Hug" and uptempo "Soul" (a Korean version of their first-ever Chinese song, "Find Your Soul") wrap up Mr.Mr. with two showcases for the Girls' lavish harmonies, which continue to set the band apart from the rest of the K-pop scene.