nintendo released more details about the game, more precisely about the game's online multiplayer
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Light vs. Dark: Team up with other players in Light vs. Dark multiplayer mode, in which two teams of three are pitted against one another. The ultimate goal is to empty the opposing team’s health meter, which transforms the last defeated team member into an angel. The team who defeats the opposing team’s angel wins. This unique multiplayer mode tests players’ ability to work as a team while keeping the match exciting as the focus constantly shifts from dealing out damage to protecting the team angel.
Free-for-All: In this mode, up to six players (including CPU players) combat each other in a winner-takes-all match. Winners are determined by high score, heavily influenced by both the number of kills and the number of deaths.
Match Set-up: Both Light vs. Dark and Free-for-All multiplayer modes are playable through local wireless play or online for players with broadband Internet access. CPU players will fill out the roster if there are fewer than six players in a match. Duration of the match, CPU difficulty, weapons and team handicaps are all customizable prior to beginning a multiplayer battle.
Weapons and Weapon Fusion: The wide variety of weapons a player has collected in single-player mode can be used during multiplayer matches. Players can also earn additional weapons as rewards in multiplayer play. Players can choose set combinations of weapons and powers before entering into a match. This provides further incentive for players to continue collecting different and more powerful weapons as they play through the single-player campaign. Players can also fuse weapons together at the Arms Altar. Fusing two weapons will result in a single, more powerful weapon that retains some of the key benefits of each, giving players the ability to customize weapons to match their play style. Fused weapons can also be used in multiplayer matches.
StreetPass: Through the StreetPass functionality of the Nintendo 3DS hardware, players have the ability to share one of their weapons with other Kid Icarus: Uprising owners. The selected weapon is turned into a Weapon Gem. Shared Weapon Gems can be converted into real weapons by paying Hearts. Players can also fuse Weapon Gems together by paying Hearts to create a more powerful Weapon.