Quad in a Quad

The BLUE quadrilateral is inscribed in the GREEN quadrilateral. The points E, F, G and H subdivide the sides AB, BC, CD and DA respectively all in same ratio. Call this ratio r. You can vary r by dragging the GOLD dot. How does the ratio of the areas vary with r? You can vary the quadrilateral ABCD by dragging the WHITE B, C and D dots. Can you explain why if r is kept fixed and ABCD is varied by dragging the WHITE dots, the ratio of the areas of ABCD to EFGH does not change?