Guides

Short reads on area, maps and cuts, and how to get better at DemiSemi.

Why we’re all bad at judging area : Your eyes compare lengths, not areas. Here’s why splitting a shape into two equal halves is so much harder than it looks.
A perfect 50/50 is always possible. Here’s the proof. : Whatever angle you pick, a perfect cut exists. The intermediate value theorem explains why, and the ham sandwich theorem takes it even further.
Going through the center isn’t enough : Does a line through the middle of a shape always cut it in half? Sometimes. The humble triangle shows how aiming for the center can land you a MISS.
7 tips for cleaner cuts : Cut where the shape is narrow, trade bumps for bulges, never forget the holes: seven simple habits that will get your cuts closer to 50/50.
Why maps lie about size : On many world maps, Greenland looks as big as Africa. How the Mercator projection warps area, and how DemiSemi draws its countries and states.
How DemiSemi scores your cut : The shoelace formula for area, the Sutherland–Hodgman algorithm for the cut, a binary search for the perfect line: the whole calculation, in plain English.

From the same maker : RicRac. Seven questions a day. Stop the counter as close to the answer as you dare, without going over.