That's a good question. First, a local multiplayer game mode will add a certain social aspect to the game, which will ultimately be fueled by the fast-paced nature of the game. To increase the playability of the game, stages will randomly generate new obstacles (walls, ladders, vents, windows, etc.) to constantly supply the player(s) with new arenas to fight in. The art style of the stages are planned to change as the game progresses, and new powerups and enemies will be introduced as the game goes on. On top of all this, the difficulty will increase to provide more of a challenge to the players as they progress through the levels. There is also talk of adding some rare special stages, like "Ninja Madness!" which will cause hordes of dextrous ninjas to spring out of nowhere to defeat the player(s) in an onslaught of shurikens and wakizashis.