Let’s take for example Farmville social game. Many clones have appeared and they have very similar concept, most of them have in the same way Neighbor, tools, etc. So legally, where is the edge of how much concept can be copied. Or is just like that the concept can not be legally protected but only a design?
It would be logically that this could be protected. But how, what can be protected here? Also in web portal you could say that others are not allowed to copy the same registration process for example, but every x portal has it the same.
If the graphics and code running the program are different, and there are no trademarked words or copyrighted text being used, there is a pretty good chance you are fine. However, anyone can sue you for anything, so you just need to make sure you have put some thought behind what you are doing.
IANAL, but yes, game concepts are not trademarkable nor copyrightable. Characters, images, etc, are.
EG – you could make a game where you threw small animals through various objects to kill other animals using either small animal or the environment. But you couldn’t call it angry birds nor could the small animals or the big animals use the same sprites as Angry Birds.