Game screen too big

The game I am using has a screen way, way to big and I cannot get out of it. I can get to the end of the screen by scrolling down and up and I tried using 'control & scroll', but nothing changes. I have tried clicking all round the edges of the game but my task bar & dock don't show. There is no 'exit' button

on the game either. I tried closing the laptop down and left it for 30 minutes but it was still there. This is on a brand new MacBook Air 13 inch.