Something looks weird with your class files. They need to be in the package folders in the jar, and you shouldn't be using classes without at least one package. In the past, I have had trouble getting code without any packages to work like this. It seems like something is wrong, because I see your game is called Game, but I also see a Game folder in the jar screenshot.
Game.class is the entry point. I have another folder called "Game" and that contains an image for the gameover. I guess I should change the name of the folder to avoid confusion