Math as art, physics as humility

Some formal systems are powerful enough to talk about arithmetic, but cannot prove every true statement about arithmetic from...

A starter note about how humans estimated huge distances with simple observations and geometry.

You cannot see the cards. You still need to make two piles with equal face-up cards.

Some operations change many things, but one parity fact stays fixed.

A note on the beauty of computer science ideas, written for people who think art only lives in paintings or songs.

A categorized guide to puzzle techniques so readers learn the trick, not only the answer.