Start Menu

- The game should start up at a start screen.
- There should be options (buttons) for playing the game, seeing the instructions for how to play, credits, and a button to exit the game.
- The menu should be composed mainly of UI elements.
- The game should transition to the play scene upon pressing the "Play game" option. The "Exit" button should quit the game entirely, and the credits and how-to-play buttons should transition to a text box with relevant content.
- Pressing the escape key on the credit and how-to-play screens should deactivate the screen, showing the original start screen.
- Method of selection is up to the implementer (this can be something like a mouse click on a button).