Slow down, you need to be a bit more specific than that.
1) Make and model of the screen?
2) What do mean by "game mode"?
3) What program were you running at the time?
4) Was the button you pushed the "-" button on the keyboard, or a button on the screen itself?
5) Is the screen "small" as you put it for all programs or only a particular one (i.e. the one you were running when you pushed the button).
The more information, you provide, the better we can help you.