Exactly One: Logic Puzzle

One pebble in every row. One in every column. One in every territory. No two may touch. Exactly One is a polished, tactile logic puzzle built for short sessions and increasingly challenging boards. Each board is split into territories. Place pebbles so every row, column, and territory holds exactly one — and no two pebbles touch, not even diagonally. The rules are simple and you learn them by playing. The first boards teach you in seconds; later boards demand real deduction. EVERY PUZZLE HAS EXACTLY ONE SOLUTION Every board is solver-verified to have a single valid answer, so you can always reason your way to it. No guessing required. FEATURES • 100 solver-verified boards, from gentle warm-ups to demanding grids • A new daily challenge with streak tracking • Instant feedback when pebbles conflict • Unlimited undo and one-tap reset • Hints that show you the next logical step without playing it for you • Game Center achievements and a daily leaderboard • Play fully offline — your progress is saved on your device Tactile territories, satisfying pebbles, and a clean “aha” every time the board clicks into place. From Knowlly Games.