Best game ever! I love how the story unfolds! =P
Grats on your first game!
Nice, simple mechanic. The control(s) work(s). The sounds are cute. :)
The menu of a game completely controlled by keyboard should probably not need a mouse to be controlled. ESC to pause the game would be nice, too.
It would also help to show the final mugs on the (missing) game over screen. They are displayed, but now I need to count them myself anyway to get my highscore, because they are instantly gone.
My highscore: 10 mugs
PS: You also have a Nullpointer in MenuScore.Start()