[filoeleven]

Sudoku variants, and even more importantly human-designed puzzles, are where all the fun is.

I grew bored with classic machine-generated sudoku ages ago because it began to feel very mechanical. Adding variant rules like thermometers lets puzzle setters use more bits of logic that are satisfying to reason about.

Puzzle creators are still finding new theorems about how sudoku works, even within the standard rules, and creating puzzles that teach them to solvers. The Phistomephel Ring, an extension of set theory, applies to every single sudoku grid in existence.

As a middling solver, many recently-featured puzzles are too difficult for me, but it’s still fascinating to watch CTC solve them.