Fridge open door detector

Our fridge door sometimes doesn't close completely. To become aware of a not correctly closed door immediately (instead of after a night) I created this open-door-detector.
As a side effect you also get a beep-notification when making your choice while the door is open takes too long ;-)

The door open detection is done by a micro switch. It closes on opening the door and thereby provides power to the circuit which contains an Arduino based microcontroller (ATmega328) and a spare piezo speake