Head-Up Nav turns your smart phone at night into a display reflecting speed and driving instructions on the windshield.
Head-Up Nav needs access to notifications in order to show driving instructions. Make sure that you allowed it in Settings -> Security -> Notification access.
For Android Lollipop (5.0) it is
Settings -> Sound & notification -> Notification access
After everything is set up just tap on navigate button to start your trip
Set your destination and start navigation in your favorite Google Maps
Tap on Head-Up Nav icon in Google Maps navigation window
Flip the screen by tapping on it. Head-Up Nav automatically creates mirror image suitable for reflection
Place your smart phone on dashboard to see reflection of the screen on the windshield