You know, it occurs to me now how similar yesterday's idea is to Mask of Majora, especially with puzzle solutions requiring you to wait for the very last second before restarting the timeline. Having an expansive knowledge of games can be a double-edged sword in this respect, since the creative process of imagining a whole new game can be hijacked subconsciously by vague and distant memories of playing a similar game years ago.
Instead of starting another game idea from scratch at this point, I'll be using the true and tested method of the creative displacement of a not-entirely-original idea. Because I'm a hack you see. Creative Displacement is simply thus: I take my-idea-that's-similar-to-another-idea, and change it cosmetically until it barely resembles the original idea at all. The sci-fi setting alone was a good start for allowing folk to be none-the-wiser of where the idea originally came from. All it needs now is a completely different interface and possibly a main character called Knil.
But seriously, there are various ethical designer codes that prohibit this kind of thing. Well, actually, there are none that I know of (like I'm even an expert of what kind of ethical pacts real designers have) but I figure there should be. But then again there are really clever features I see in games that decide to keep it as their own, using it as that particular game's own unique identity instead of using a combination of narrative, gameplay and graphical factors to define itself like most good games do. In the gaming world, the story doesn't often make a game unique but rather a clever game mechanic or feature does. I still believe those ideas should be open to anyone to use, providing some level of originality is intended with their use.
For example, the original Metal Gear Solid, while having an amazing and complex plot (the cutscenes of which do tend to take up a lot more of the game time than they strictly should) really got to where it was by having a clever and advanced stealth feature to focus the gameplay around. I can't even begin to list how many titles have taken that "unique" stealth feature and either tried to do something new with it (appreciating the concept from a designer's perspective) or simply tried to cash in with mimic games using the feature at the height of its popularity (appreciating the concept from a marketer's perspective).
Beyond Good & Evil is an example of using a stealth system similar to Metal Gear Solid in a new way, as you play a relatively weak (though she can kick ass if she needs to) journalist who needs to sneak around the heavily-armed guards and take incriminating photos of their operations. While several factors of that game are derivative, as are most features in any video game ever ("all FPSes are clones of Wolfenstein 3D!"), the interesting and innovative uses of those factors employed by the game meant it received glowing reviews by the industry in general.
So, in conclusion, should a unique game feature be used by others for new games? Yes and no. While there's no copyrights against a certain game feature (though I wouldn't be surprised if FFX's Sphere Grid has its own copyright), there is the reputation of taking such a move to consider. But if you can do something imaginative and awesome with that idea, maybe better than the original game did, then it shouldn't matter if that particular part wasn't invented by you. It's like inventing a time machine by using tools someone else invented and a basic idea from an old sci-fi novel that was never fully realised. Does that still mean the time machine is yours? Hell yes.
But still, it is kind of cheap. There needs to be more true innovation (if there's any left) and less taking ideas and changing them slightly for a game that's sufficiently different from the original to warrant it's own identity. The true innovation stuff is harder than it sounds though, trust me.
