"Battle Mode" includes content from the game's Nintendo GameCube port, Sonic Adventure 2: Battle. The DLC adds six new characters to play as, 21 two-player versus maps and the Chao Karate fighting mini-game in which players can train their self-bred Chaos critters against A.I. opponents.
Steam users can snag the game for $9.99 and the DLC for an additional $2.99.
Sonic Adventure 2 along with its DLC was ported to PlayStation Network and Xbox Live Arcade last month along with Nights into Dreams HD as part of the Sega Heritage Collection series of games. The game was originally released in 2001 for Sega Dreamcast as part of Sonic the Hedgehog franchise's 10th anniversary celebration.