NOTE: You can download the individual movies from here.
In the original GEOr task it is perhaps quite easy to discern that a quarter of the square is overlapped. Finding a justification for this is more challenging, but, as we have seen, this can be done in various ways.

For the variant that we considered, where one of the shapes is a rectangle, the size of the overlap varies. In the above task (GEOs), the size of the overlap is constant again. What happens if we replace the triangle (or the hexagon) with a suitable-size square, say?

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