Quadrilateral Interior Angles (Revamped)

Interact with this app for a few minutes. Then answer the questions that follow. Note: ALL LARGE POINTS are moveable.

What do you notice here? What do you wonder?

Try to get the vertices of the 4 angles to coincide (lie on top of each other). Move these sectors (circle pieces) around so they don't overlap. Notice anything interesting? If so, describe.