Knight (Mind Loft)

Knight adds one rule to classic 9x9 sudoku: the same digit may never sit a knight's move apart, two squares in one direction and one square across, as a chess knight jumps. Rows, columns and 3x3 boxes still hold 1 to 9 exactly once. Nothing extra is drawn on the grid; selecting a square lights up the eight squares its knights reach, so you never have to picture the L shape.

The knight rule reaches across boxes instead of inside them, and it does so much work that the board can print far fewer digits than an ordinary sudoku. Every board has a single solution reachable by logic, and the knight rule is always needed: read as a normal sudoku, the same clues would fit more than one grid. Wrong entries are not flagged, and a clean solve scores 10 with the leaderboard decided on time.

Printed digits fall from 28 on Monday to 16 on Saturday, and the Sunday Edition prints thirteen. Below the grid sit Notes, Auto-move (which steps to the next square after each digit), Undo, Erase, Clear, a Hint and Reveal & end, and each number key shows how many of that digit are still to place. A new board appears every day at midnight Eastern.