Core is a new game creation platform built upon Unreal Engine that recently went into open alpha release. Core is a game creation platform in a similar vein as Dreams, Roblox and Second Life. It comes packed out of the box with models, audio and materials and can be coded using the Lua programming language.
Core is described as:
Core is an endless universe of games and worlds designed by a global community of creators. It's a radically accessible game construction kit, content exchange, and game-playing platform, all in one. With Core, you can create multiplayer games, using the power of Unreal Engine, with no coding or art skills required. When you're ready to share your creations, publish them to the Core platform where they'll be instantly available to play.
Core is in Open Alpha which means anyone can start building, sharing, and playing games. However, Core is not complete, and we will be adding several features and making improvements over time.
Plans exist to add monetization, enabling creators to make money with their Core creations. There is also the possibility that Core games will be publishable to other platforms, but for now Core games are published on the core website. Core is well documented for developers, with that documentation available here. Words do a poor job of describing Core, watch out the video below to see Core in action.