For the game, BioWare changed several gameplay elements and further emphasized third-person shooter aspects, including limited ammunition and regenerable health. In contrast to the exclusive focus on the main story of the original Mass Effect, the developers opted to create a plot where optional missions had as much intensity as the main mission. Mass Effect composer Jack Wall returned to compose Mass Effect 2's music, aiming for a darker and more mature sound to match the game's mood. Mass Effect 2 also supports a variety of downloadable content packs, ranging from single in-game character outfits to entirely new plot-related missions. Notable packs include Kasumi – Stolen Memory, Overlord, Lair of the Shadow Broker, and Arrival.