Ideas are everywhere for games, products, algorithms, etc. In hypothetical terms, let's say user number x posts on (insert social media site here) that they would like to see a game about (insert game topic here). Can I take their idea and formulate it into a game without giving them any credit?
An idea isn't protected by United States copyright law, and ideas are stolen by entrepreneurs often. To quote 17 U.S. Code § 102:
(b)In no case does copyright protection for an original work of authorship extend to any idea, procedure, process, system, method of operation, concept, principle, or discovery, regardless of the form in which it is described, explained, illustrated, or embodied in such work.
This means that an idea is not in a tangible form (or a copy), and is perfectly able to be taken by you without any legal repercussions. It explicitly states an idea cannot be copyright protected.