In the sea of nav-light apps, Lights and Shapes is a particularly useful one. It's a simple app that not only explains the different requirements for nav lights and day shapes, but shows you them — in 3D — which gives you a much better representation of what you'll see while your on watch. You can rotate the 3D image to any angle, so you can see what the lights look like from any point of view. Very cool. There is also a built in quiz so you can test your knowledge. Check it out!