I'm not a lawyer, but you can't copyright ideas or mechanics, only specific expressions. So unless you're literally copying the code that does what you want to do, you should be in the clear. I copy mechanics from other games all the time, as do AAA game developers. After all Nintendo didn't sue SEGA for controlling Sonic's jump height by how long you hold the button.

Julie nailed it.

You cannot copyright an idea or a concept. The code to that mechanic can be copyrighted, so as long as your developing the same concept or mechanic without using the same code or assets generally speaking you'll be fine.

6 minutes ago, 1024 said:

You may not be able to copyright a game mechanic, but you sure can patent elements of games. Some typical examples that are (or were) patented include "minigames during loading screens", "Mass Effect dialogue wheel",  "the Crazy Taxi arrow above your car that shows you where to turn", "Katamari rolling and picking up stuff" etc. Be careful when you say "Oh, it can't be protected, just do it yourself"  

Careful citing older patents, since Alice Corp. CLS Bank International was deiced getting a patent for software is incredibly difficult, and some of these patents you cited can be challenged and throw out because of the courts holding.

Please be careful citing any patents. Knowing about a patent makes you liable for triple damages should you violate it, so by citing patents you could be putting software developers in jeopardy. The only examples you should ever cite are expired patents, like the patent on natural order recalculation (i.e. permission to make a spreadsheet program that functions correctly).

There is nothing a software developer can realistically do to avoid infringing patents. There are too many, and it's too hard to tell what patents could possibly apply (e.g. that natural order recalculation patent was on the face of it about compilers, and yet it was used against a spreadsheet developer). All we can do is close our eyes, never look up patent information, and hope we don't get sued by patent trolls. And in the long-term, software patents need to be abolished.