This project is an original application of a digital clock with mirrored display and driven by Arduino and accelerometers.
With this clock it is possible to place it in front of a mirror and the image of its display will be shown in the correct position, automatically canceling the mirroring effect !!!
This principle is the same as that used in HUD (head-up display) for mirror surfaces or glass, such as on car windshields and aircrafts.
Let’s see how it works !!”

Link