Hi HN! I wrote a small file that solves sudoku puzzles at the type level - that is, entirely within TypeScript's type system, with no runtime code.

To play with it, scroll down to the bottom (below where it says "BEGIN TESTING") and check out the examples. You can "run" the solver by hovering over the name of the type (e.g. SudokuEasySolved).

Also, if you haven't seen it already, I did the same thing with Conway's Game of Life: https://news.ycombinator.com/item?id=37438028 :)