Stone Sudoku

Medium difficulty sets the pace from the first grid. In Stone Sudoku, more than 400 puzzle layouts use a 9x9 square filled with pebbles shaped like digits, giving the board a stone look instead of plain numbers. Standard Sudoku rules stay intact. Empty spaces must end up with digits 1 through 9, and no number may appear twice in the same row. The same rule applies to each column. Every 3x3 block follows it too. The layout suits players who already know classic Sudoku, and it also works for newcomers because the rules never change.

How to play?

Drag digits from the main number row onto empty cells when you're ready to place an answer. A second row holds marked numbers for cases that need temporary notes during solving. The back arrow removes the last action if a placement needs to be undone. The right arrow finishes the puzzle. Final checking happens only after the grid is filled, and the check button works only at that point. Hints are absent. Error correction is absent as well. Settings don't appear here either. One wrong digit can invalidate the whole board. A failed solution sends the puzzle back to a full restart.