The items on this TODO list are sorted descending by priority:
	- Gun sometimes fires two bullets although the up button is only pressed once. This has to be fixed.
	- Better graphics are necessary.
	- Sounds have to be added to the game.
	- Joystick support.
	- Mouse support.
	- User-configurable game controls.
	- A highscore has to be added.

	- Retro mode, in which the game looks, sounds and feels like th original.
	- Translations might be nice when the amount of text has increased.
	- ...
