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Transition Windows.
Think transition lenses except windows. Also, instead of just tinting, the windows can frost or reflect (mirror) automatically or through a manual adjustment via an app or home panel. The technology would allow for increased energy efficiency, privacy, and the creativity to transform space within a home, office, or classroom. No more expensive drapery and bulky curtains especially for small spaces.
Inspiration here is probably a bit from that Smart House movie on Disney back in the 90s (although they definitely did not have these windows) as well as always living in small apartments in my adult life and never investing in blinds or drapes like the millennial I am.