Can you patent your video game mechanics? Like if Flappy Bird mechanics had been patented by the guys who made the helecopter game (original flappy bird), could the creator of Flappy Bird be sued for it?
This is a complex question because of changes in patent law relating to three significant cases, namely Bilski, Alice, and Mayo. The ultra-short summary is that these cases pertain to the question as to whether a purely abstract idea, such as a set of mental steps, is patent eligible. (This is subject may referred to as "post-Alice", because that was the big one relating to this specific issue.)
Thus, can you patent the idea of a virtual object moving up and down in the context of a video game, such as in the classic arcade game Joust?
It was surely not the intent of the patent review board to remove this traditional method of protecting game mechanics. Rather, the new uncertainty can be viewed as fallout from Alice. But it is not clear that pure mechanics that form novel games are no longer patent eligible.
Depending on which patent attorney you speak to, you will get answers ranging from "no" to "yes" to "maybe". It seems as though patent attorneys who consider such patents to still be viable find value in tying the mechanic into a device, such as a computer system, though that, on it's own, is not enough.
I would urge you to read this very recent article from IP Watchdog.
The one comment I will make on the article is that my personal feeling (not as a patent attorney but as a game designer) is that the Smith's patent, which is causing such a stir, may not have had a great deal of merit. I suppose, in the loosest definition, their method of wagering could be a "game", but it required a pre-existing game to function. It might be analogous to trying to patent a method of betting on Chess, which, before Alice, may have been possible.
It is also important to note that a patent is not a monolith, being comprised in most cases, of a series of claims. Each claim is reviewed individually, and the rejection of one claim does not necessarily mean that all claims will be rejected.
A recent game that may be helpful to consider is Threes!, aka 2048. Would it have been possible to patent that game mechanic? Quite possibly. The more relevant question may be would it have been worthwhile to pursue a patent, which can be a fairly expensive process. (Based on the number of times the clones have been downloaded, I'd lean towards yes, but in this context, it is really an assessment of risk vs. reward.)
The other thing to be aware of is this recent case, Spry Fox vs. Lolapps, which seems to extend protection of game mechanics into Copyright law. It could be overturned at any time by a higher court, but word on the street is it is a kind of "third rail" and no one wants to go near it. Further, there is some precedent for this extension of Copyright law in Tetris vs. Xio, which is bordering on Design Patent territory.