CDE Humble Gaming was at WWDC 2010 showing of their upcoming trading card game Arena 9. Game developer and long-time Magic: The Gathering player Jeff Lyndon described how they were trying to create an iPhone suitable experience for a collectible card game.
High amongst their priorities was an accessible game that was easy to learn, but also one that didn't overwhelmingly advantage those who had simply collected better cards. The game revolves around a collectible cards that are earned by the user. An initial set is provided, but over time, new cards can be collected by earning in game experience or through in-app purchase. Cards are organized into 5 card decks that you can take into battle.