Since there won't be any new puzzles for two weeks, I decided to post something a little more time-consuming. I was anonymously sent this weird crossword last week... and I don't know how to solve it! Help!
(Note: I was able to complete some first steps, so feel free to ask for hints. But at some point, you'll have to figure out how to go farther than your teacher could. Such is life...)
These three animated GIFs all appear on the Wikipedia page for what invention?
Solution
Sewing machine. The GIFs demonstrate different kinds of stitches.
Congratulations to yesterday's solvers Rachel, Milo, Lucia, Alex Z., Lemonade, Yana, Kalpana, Charlie, Jacob C., Maddy, Anna J., Anna K., Kate, Mr. Gregg, and Jason. Thanks to everybody who made a guess!
Ten years later, Dr. Shapiro revived Puzzle of the Day at Proof School, writing each day's puzzle on a name tag. After 600 puzzles or so, he was just starting to feel normal about students reading his chest all the time when campus closed and the puzzle, like the rest of our lives, moved online. New puzzles are posted daily on school days.
Want to catch up on old PotDs? There's an archive currently containing puzzles from March to December 2020.