This Numberphile video is ostensibly about creating a computer from 10,000 dominoes, but to get there it goes through an impressive amount of basic (don't worry, very basic) math and engineering to make sure everyone is up to speed.
Sure, the video is 18.5 minutes long, but if you don't remember binary, circuit diagrams, or anything about logic gates from school, you're going to relearn it here—painlessly. Sometimes it's kind of mind-blowing to take a step back and think about what a computer is in its most simple form, and how basic mechanical operations underlie everything our laptops and smartphones do.
Even if you already know about all of this, seeing a computer laid out in dominoes is pretty great. Especially because the 10,000-domino chain reaction can add any two four-digit binary numbers and return a five-digit binary sum result. Not bad for some hunks of plastic.