play fast-paced levels, emphasizing platforming. Their homing attack can lock on to robots created by Eggman and G.U.N., and they can grind on rails. Tails's and Eggman's levels are slower and oriented towards multidirectional shooting; they are confined to mechs in which they can jump short heights, hover and shoot enemies. Knuckles's and Rouge's levels are open and feature action-adventure gameplay with treasure hunting; in each level, they must find three shards of the Master Emerald. Their search is guided by radar and puzzle-based clues from harmless robots. Knuckles and Rouge can glide, defeat enemies with punches and kicks, and scale walls, digging into them to find power-ups. Adventure 2 has the health system found in many other Sonic games. The player collects rings scattered throughout the levels; being hit by an enemy while holding rings causes the player to drop them all, while being hit without rings causes them to lose a life. Tails and Eggman have health bars, which are slowly refilled by collecting rings. Dying with no lives results in a game over screen. The characters can obtain permanent upgrades that grant them new abilities; for example, one upgrade allows Sonic and Shadow to dash along a sequential trail of rings to reach distant platforms, one gives Tails and Eggman hover jets that slows their descent in order to cross large gaps, while another lets Knuckles and Rouge dig into the ground to uncover treasure and Master Emerald pieces. Separate from the main campaigns, the player can raise Chao as virtual pets. They have five attributes (Swim, Fly, Run, Power and Stamina) and a moral continuum from Hero to Dark. From the moment they hatch, their stats can be increased with Chaos Drives or small animals, found in the main stages, which empower them to compete in karate and racing minigames. Their alignment gradually changes based on their affection for the characters; for example, a Chao which likes Tails will gradually become more heroic. Playing with Chao increases affection, and when a Chao becomes fully Hero or Dark, it assumes that form permanently. Although Chao eventually die, if they receive enough affection during their lives they reincarnate. Adventure 2 has 180 emblems, earned for a variety of tasks. Each level has five missions; only the first is required to continue the campaign, and other missions include completing a harder version of a level and collecting 100 rings.