Whenever you work on 2D games, one of the most common concerns is whether your GUI will look good on every screen resolution, or if things are going to be in the place you expect them to be.
Another issue that pops into mind, is fairness. As some devices have more screen space, meaning more playing area, this would signify an advantage over other players. Obviously this depends entirely on the type of game you are developing as it can just mean more dead space.
If you are working on a platform that scales things automatically, maybe this is not an issue, but if not, you must handle this issue manually.
In this article I will talk about aspect ratio conservation and automatic scaling for 2D games on OpenGL, this will help keep thing in place and help artist design everything to a specific aspect ratio.
Code will be applied to an OpenGL environment but the concept can be applied to any framework/engine that lets you modify the viewport.