Proof of four triangles with equal area.

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I have been working on proofs without words but I have a bit problem about Steven Snovers proof. It proves that these four triangles have equal area. Proof comes from rotation but I couldnt get it. Snover's proof

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That's a nice proof concept, but it does need just a little thought.

Consider the three triangles made up of the central triangle and one of the new triangles. In each case, the new triangle shares the height and owns half the base (when calculating area from the shared base). Therefore the areas are equal.

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A median divides a triangle into two triangles with the same area. If you consider then, in the last picture, the triangles formed by the central (dark gray) triangle with one of its neighbours, you can infer that dark gray triangle has the same area as the other three.

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After a sequence of actions, we end up with the final figure. Let us marked down all the line segments that are of length c.

enter image description here

In the final figure, the area of the red marked triangle is equal to that of the grey one because they are having the same altitude and with bases equal to c.

Similarly, the other two will have the same area as the grey one.