From what I've been reading I think that the things from the game protected by copyright are everything related to the art of the game, such as the music, graphics, the name, the text that constitutes the story within the game, etc.
There is also this approach to program code that it allows to be copyrighted as it is (ie. it protects from copying it as with copy and paste) but the way it works, whatever it does can't be copyrighted.
For protecting "ways of doing things" such as an algorithm or data formats, I believe patents can be used, but they are very different from copyright, you have to pay to maintain the patent and there are many restrictions about what you can or can't ask for patenting.
I'm not a lawyer and laws are not the same even international treaties are handled different from place to place, so if you are really concerned you should ask a lawyer. I think you won't have any problem unless you are actually copying original things which are noticeable for someone who doesn't know about game development, because afaik game mechanics can't be copyrighted.