"Monomino" – the most difficult eight-letter English word to type correctly on a QWERTY keyboard? (I consider myself a decent typist, having in fact won my first college scholarship in a typing competition. I still type stuff like monimon and monimono every time I try to get this word in print - which is many times per day thanks to one of my classes)
(Obviously a+b+c=abc has lots of real solutions, but not too many small values with short decimals)
A post at Wolfram blog tells a biographical story of a figure whose name I don't even recall hearing before:
Passed level 23!
It's a bit difficult because you can't see the whole picture so that you can't plan at the first time. In addition, even if you planned, its perspective changes and messes up your planning.
Levels stuck me or I think worth trying: 5, 14, 18, 22, 23.
And especially also this one.
Create an account, create a password satisfying baroque rules, click to opt out of spam, click to decline cookies, click to acknowledge that declining cookies will log me out, click to accept cookies, enter a redemption code from email, view textbook in clunky viewer coded by monkeys that do not read books...
or just download the readily-available pirated pdf
(or – imagine it – mail me a physical evaluation copy like you used to)