Off topic, a little bit. Is aliexpress legit? I believed it to be a spamtastic bait-and-switch ripoff scam, until Kepis mentioned getting something decent for a decent price. Comments?
Back on thread, my high school physics lab included a 0.5 m front-surface parabolic mirror. We did stupid things with it, of course.
Still on thread, there's a sequence in The Walking Dead where Daryl and some soon-to-be-dead character strip the headlight assembly from a car and later use it to start a fire in what appears to be a Dakota fire hole.
<humor>That is the only real-world application ever to appear on tWD, imho. OK, that and "know what you are shooting at and what is _behind_ it." Sucks to be you, Coral.</humor>