The demand for "natural light" in homes and offices is very high, and higher than the availability of actual daylight. And there seems to be a pretty feasible way to create a fake window (a light panel that mimics sunlight through a window), using LEDs and a fresnel lens. There's no shortage of videos around showing how to DIY such a thing, such as https://www.youtube.com/watch?v=8JrqH2oOTK4 and https://www.youtube.com/watch?v=GDeEuzKXCH4So, why can't I find many such products for sale? There are a couple of high-end companies like https://www.coelux.com/, but where's the mass market stuff? Is there an opportunity being overlooked here, or am I just missing something?