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How about a venitian-blind? When you want to look out and not be seen, just tilt the blades.
If you want to see scenery at one vertical angle, and want to hide from someone at a *different* angle, you can do it that way.
(Yeah, you get only horizontal "stripes" of the view, but that's the cost, like "there's no free lunch".)
And you don't like looking through the window via those stripes, well, you can just jump up and down in the shower, fast enough that it blurs into a full picture!
Hell, you can even put one of those small circular tramplines in the shower!
David