The addition of a couple of extra chess-move constraints makes for a sudoku defined by two digits, 1 and 2, carefully placed, to present one unique and reachable solution. webapp 
YOUTUBE yKf9aUIxdb4 Published May 10, 2020.
We're Simon Anthony and Mark Goodliffe, two of the UK's most enthusiastic puzzle solvers. We have both represented the UK at the World Sudoku Championships and the World Puzzle Championships.
We're also "cryptic crossword" aficionados. Mark is the twelve-time winner of The Times championship and Simon is the former record holder for most consecutive correct solutions to The Listener crossword. We hope we can help your puzzle solving while also introducing you to some of the world's best puzzles.
# Prolog
Since Prolog is a declarative language, writing a Sudoku solver is remarkably concise. In essence, all the programmer needs to do is define the constraints of the game, and Prolog is smart enough to find solutions. post
To write a solver for the Miracle Sudoku puzzle, we need to encode four rules.
Normal Sudoku rules apply.
- All rows/columns must contain 1..9 exactly once. - Each 3x3 block must contain 1..9 exactly once.
The selected chess rules that beautifully constrain the solution.
- Any two cells separated by a knight's move or king's move cannot contain the same digit.
Finally one more constraint on adjacent cells rewards working forward digit by digit.
- Any two orthogonally adjacent cells (i.e., cells sharing an edge) cannot contain consecutive digits.
# More
Sudoku authors compete to develop more "miracle" puzzles.
YOUTUBE Tv-48b-KuxI Published May 17, 2020.
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I wrote a simple possible next move generator based on a board configuration encoded into a url. I'd like to add these extra rules and see if I can duplicate the sequence from the video. wiki
I might rewrite my solution in client-side javascript first. I notice that the Cryptic guys offer a react-based tool and probably used that when making the video. page