Stones: Gravity Puzzle

One square left or right, then gravity takes over. Same colors dissolve. 350 levels in seven sets. Set 1 is free. No ads, no subscription.

You push a stone one square to the left or right. Gravity then pulls it down until it rests. When two stones of the same color touch, both dissolve. A level is solved when the board is empty.

THE RULES Each move shifts exactly one stone by one square, left or right. Everything else follows automatically: the stone falls until it rests on another stone, a wall or the floor. If two or three stones of the same color then sit next to or on top of each other, they dissolve, and whatever was above moves down. This can set off chains. Walls are fixed: they can neither be moved nor removed.

Moves cannot be undone. The only way back is restarting the whole level. One misplaced stone can make a board unsolvable; when the app can tell for certain, it says so. Thinking ahead is the core of the game.

350 LEVELS IN SEVEN SETS Every level ships with a stored solution and a known move count. The difficulty model that orders the levels is built from these solutions. Most boards were fully searched for it; a few very large ones carry an estimate from the same model. Stars: three for the shortest known move count, two for up to 25 percent above it, one for solving. Using the built-in solution help means no star for that run.

THREE MORE STONES Skull, in SET 5: skull stones must still be standing at the end. If two touch, both are gone and the level is lost. Rainbow, in SET 6: the rainbow stone takes on the color of its neighbors once they all share one. A second rainbow next to it blocks that. Wood, in SET 7: wood breaks when something falls onto it or when it falls itself. Pushing it sideways does not damage it. At the end the wood has to be gone as well. SETS 5 to 7 start easy again; each set has its own difficulty ladder.