The main screen shows animations of 3D shapes. A video player control allows you to play/pause an animation in which the shape rotates in different planes and folds and unfolds, so as to show both the 3D shape and its net. You can scroll through the animation so that you can easily show key points.
Click Set up to choose different shapes, and whether 1 or 2 shapes are shown on the main screen.
Clicking Reset undoes all changes you have made, returning the tool to its default state.