Dr. Light: Now, as you may have noticed, there is but one button on the time machine. You can access different functions by varying the amount of pressure, duration, and frequency of button presses. To access the main menu, lightly tap the button...
George: Wait, why not just have more than one button?
Dr. Light: For simplicity of use, naturally. Now, to access the main menu, tap the button lightly twice, then slowly three times, then twelve times at medium-fast...
Twenty minutes later...
Dr. Light: ...but whatever you do, don't press it really hard, or you might activate the auto self-destruct.
George: You know, maybe I should be writing all this down...
Rose: (trying to get the Doctor out of manacles with the sonic screwdriver) What do I do?
Doctor: Just flick the switch! (manacles open)
— Doctor Who, "The Long Game"