Topic: The Last Stand: Dead Zone /
This game idea stolen from Rebuild 2?
So to answer the original question.
Ideas cannot be protected with patents, copyright, or trademarks.
Copyright protects the “expression” of an idea, not the basic concepts. Thus you can write a story about a school for wizards without getting sued by JK Rowlings (sorry successfully sued), but you cannot write a story about Narry Dotter who has a mark on his forehead without appropriating the “expression” of the novels.
Further you cannot copyright genre tropes, known as scenes a faire in copyright talk.
While the two games share some source material, this game does not appear to utilize the expression of rebuild 2 and so does not violate its copyright.
disclaimer: I am not a lawyer (yet) this is not a “legal opinion” and is worth exactly what you paid for it, i.e. zip, nada, nothing, etc.