We wrote this in perl on a long flight. Years later converted to deno, added samples and forced moves, then squeezed it into a Frame. github 
The small library of sample puzzles is in the source.
The interactive game displays within the Frame.
This page helps you solve sudoku puzzles by showing choices satisfying two simple rules: at-most-one and at-least-one
of every digit must appear in every row, column and square.
Include a working example if possible.
http://ward.dojo.fed.wiki/assets/pages/sudoku-helper/sudoku.html HEIGHT 520