Varignon's Theorem Animation

Move points A, B, C, or D to begin.
1) What are points E, F, G, and H? 2) What do the colors (red, blue . . . ) signify? 3) What is the yellow point tracing? 4) Why are the marked segments parallel? 5) What other relationships are there? 6) How small is the interior shape compared to quadrilateral ABCD?