Screen size for steam

Hi, I already start creating my game 640x480 screen size and I wan't to publish it on Steam. Is it a good size for steam to run on full screen mode? If no what should I do?

There's no "correct" size for Steam. Most monitors and tv's are 16:9 aspect ratio, so if you want your game to fill the whole screen for most people then you can adjust your game to be 16:9, but other than that there are no rules and you can just do whatever you feel like.

Then I publish (flash) and run it in full screen mode I just see a black screen, then I test game  in fullscreen mode my all tiles dissapear. I'm afraid to do not have same issues then I finish game and try public it on steam.