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John Scholes builds a depth-first tree-search operator step by step in a Dyalog APL session. It covers higher-order functions and runs the search on the N-Queens problem.

A University of Michigan Medicine demonstration of building a cheap DIY air purifier from a box fan and a HEPA or high-MERV filter using hardware-store parts. It explains why this helps against dust, smoke and viruses and ties it to local air quality readings.

Terry Moore's three-minute TED talk showing a better way to tie shoes, replacing the common granny knot with a square knot so laces stay tied.

DIY Perks shows how to turn old or smashed TVs and monitors into realistic artificial window lights, using the backlight and Fresnel lens to simulate distant daylight.

Essential Craftsman announces the start of a spec house build on a scenic lot, kicking off a long series. The channel covers every step of building a house from the viewpoint of a general contractor.

Lock-picking YouTuber Bill Johnson (BosnianBill) explains how to choose a high-security lock and why, showing examples and comparing designs. It covers what makes some padlocks more pick-resistant than others.

A woodworker shows how his table saw accident happened, why it happened and how to avoid a similar one. He describes severe hand lacerations from a blade contact.

A This Old House segment where Richard Trethewey installs a heat exchanger that uses waste heat from a central air conditioner to heat a swimming pool.

Bisqwit writes a raytracer from scratch in C++ for DOS, rendering in the 16-color VGA palette at 640x480. The video also covers color quantization and ordered dithering.

Jacques Pepin makes a classic French omelette in a short uncut demonstration. The video contrasts it with the American style.