I'm developing a game with Java using Slick2D and I want to make a game that could target all the recommended resolutions, as you can see in almost every game you could have an option of changing the resolution. I would like to know how game developers make their game assets once and use different screen resolutions and it still looks good.
My only guess is that when you're in game (playing-moving, jumping) the viewport of the camera is set to some size at the same aspect ratio of the player's monitor.
How do game developers do this? Not just in-game, even when just browsing the menu.