I'm new to game development, and although I am perfectly content with producing indie titles, I would also like to use them as marketing vehicles for large developers, as some of my ideas require technical expertise and sheer manpower that I don't have access to. Among songwriters, a stripped-down demo encompassing the lyric/composition is sufficient for submission to a major label; they fill in the blanks with their own studio musicians and producers. Is this method legally and economically viable in the game industry? For example: let's say I created Counter-Strike, which fundamentally alters Half-Life's gameplay while adhering to its physics engine, interface, and so on. Let's say I didn't want to make Counter-Strike a Half-Life spinoff, but rather intended to create an entirely new FPS built from the ground up. If I submitted Counter-Strike to a major developer, would they be expected to craft a new FPS from scratch and incorporate the elements which make Counter-Strike unique? Let's assume these aren't just a few interesting notions, but rather thoroughly balanced character creation/progression systems, combat engines, possibly even campaigns/characters? In other words, can I use an existing game as a template for new ideas, and expect a major developer to create a game on the strength of these concepts?