The "Extreme" game mode is strictly single-player, and has the gameplay sped up deliberately with faster enemy attacks and a smaller bullet blast radius.
To counter this, players will be able to reload their shotgun faster, as well as make use of a new melee attack feature. With the melee, a player can attack multiple enemies with a single push of the A button. Melee's can also be used defensively to block enemy attacks, missile weapons, and boss attacks.
Make sure and check out our House of the Dead 2 & 3 pictures area as we have all new screenshots from the game.