Every number has one place
Use 1 through 9 once each. A completed square has three rows, three columns and both diagonals all adding to 15. The tool checks all eight sums, rather than just one row or the overall total.
A classic, and a puzzle
The classic south-at-top arrangement reads 4–9–2, 3–5–7, 8–1–6. The page begins with a shuffled puzzle. Choose two tiles to exchange them; Shuffle makes a new puzzle, Retry returns to the start of the current puzzle, and Show classic reveals the reference.
Stone you can move
The canvas depicts original carved mineral tiles with bevels and shadows. Click the stones or use the numbered buttons; arrow keys move focus, and Enter or Space selects. Export records the current arrangement and its eight sums.