A patent represents a grant from the United States government to an individual for the exclusive right to make, use, import, sell, and offer to sell an invention. In order to obtain a patent, an inventor must prove that the invention is new, useful, and not merely an obvious improvement over what was already known. Inventions that may be patented include machines, articles of manufacture and methods of operation. Video games, virtual worlds and other types of software can be claimed as all three of those types.