Accidentally buying the wrong game would actually fall under a different area of law: Fraud and possibly trademark infringement. Though, you can't trademark (or even copyright) gameplay/mechanics...

In 1879(!) Baker v. Selden, the Supreme Court ruled that copyright protects only the expression of ideas (the text, illustrations, and phrasing), not the underlying ideas, systems, methods, or processes. This is important. The same rule applies to patents: They only cover the implementation of ideas, not the ideas themselves. Endless case law reaffirms this.

WHICH IS WHY SOFTWARE PATENTS SHOULD NOT EXIST.

I know it's unrelated, just wanted to throw it out there 😀