It is pretty nice of allowing C/C++, javascript, and Lua. It pretty cross-platform on web, ios, android, and native on various desktop OSes.
Probably a lot less capable than Unity, but maybe easier to learn. Also, more focused on 2D than 3D.
Cocos is an open source development engine. It can be used to build games, apps and other cross platform GUI based interactive programs.
https://www.cocos.com/en/