Gamekit

Adds Game Center integration to iOS games with player authentication, leaderboards, achievements, and multiplayer matchmaking. Covers both real-time and turn-based multiplayer, the access point widget, and dashboard presentation. The authentication flow is straightforward but requires checking player restrictions like age and multiplayer gaming limits. Leaderboard submissions are async and support both classic and recurring types. Achievement progress only moves forward, never backward. The multiplayer implementation uses peer-to-peer connections through GKMatch. Good reference if you're wiring up Game Center for the first time and need the boilerplate without digging through Apple's docs.