Using nothing more exotic than some bare LEDs, an Arduino, and a cardboard box, these little gadgets can quickly and easily be deployed in your windows or bushes to produce an unsettling effect ...

That’s not the only way to do it, though, as [Markus Bindhammer] shows with this proof-of-concept UV/visible spectrometer. Rather than a single light source, [Marb] uses six discrete LEDs ...