Game Center supports real-time and turn-based multiplayer functionality. When you adopt Game Center’s full-featured UI, you can provide a familiar and consistent matchmaking experience. In particular, you can offer the built-in player picker view, which helps players find people for a match without leaving your game. The built-in picker view can list system-suggested contacts, Game Center friends, and players who have recently participated in non-auto-matched games.
When you adopt Game Center multiplayer functionality, you can use the system-designed multiplayer UI or present the information within your custom UI. Although the Game Center multiplayer UI supports the ability to send invitations to a player’s contacts, GameKit doesn’t provide API that lets you offer this functionality in a custom multiplayer UI.
Provide an unambiguous button that lets players access the multiplayer lobby. If your game supports a multiplayer experience, clearly display this option in your game’s main menu screen. For best results, use the term "Multiplayer."