Solo

1. Tap a square to lay a stone on it. Tap again to mark it as staying, and once more to clear it.
2. No number may show twice in the same row or the same column — cover the copies you do not want.
3. Two stones may never touch edge to edge. Corner to corner is fine.
4. Every square still showing must stay joined to the others in one piece.

There is exactly one way to satisfy all three rules, and no guessing is needed to find it.