Main menu

Functions
A main menu is a menu that normally appears at the beginning of a game. A main menu is used to allow the player to select game modes, options, and a range of other things. A main menu generally contains these three choices:
 * play: where the player can begin the game, select a level, etc.
 * options: the player can set options such as sound volume, full screen/non-full screen, graphics, etc.
 * exit: the player exits the game.