OpenNERO is an open source game platform designed for game AI research. The software package combines features commonly available in modern game engines (such as 3D graphics, physics simulation, 3D audio rendering, networked play, and a powerful scripting interface) with an easy to use API and tools for defining machine learning tasks, environments, and agents. Flexibility and ease of use of the system are demonstrated by following the process of creating a machine learning game from scratch. The scalability of the platform is tested through the implementation of the existing NERO machine learning game using the new tools.