2D rectangle to select

[Pryme8]

Marquee selection demo

The rules. From right to left - weak selection. Object should be fully under selection square. From left to right - strong selection. Touching an edge of object is enough. Spheres (and other smooth meshes) do not work . I use edge renderer. I think in case of sphere I should use not edges but outline of mesh. But I have no idea how. If you have anything to suggest that would be super!