Questions
Stostone — ストストーン — is a Nikoli puzzle about stones that fall.
- What is Stostone?
- Stostone is a Japanese logic puzzle published by Nikoli, also written Sto-stone. Bold lines cut the grid into rooms, and you shade cells to build exactly one stone in each room. Stones in different rooms must never touch side by side. When every stone then falls straight down, they have to land filling the bottom half of the grid exactly.
- What do the numbers mean?
- A number belongs to its room, not to the cell it is printed in. It says how many cells that room’s stone covers. A room with no number still holds a stone, of any size that fits everything else.
- Can I shade the cell with the number in it?
- Yes. The number labels the room, so the cell it sits in is an ordinary cell of that room and may end up part of the stone or not.
- How much of the grid gets shaded?
- Exactly half of it. The stones fall down and fill the bottom half with no gaps, so the shaded cells and the bottom half have the same area. On a 6×6 that is 18 cells, on an 8×8 it is 32, on a 10×10 it is 50. The counter under the board keeps the running total for you.
- What does "fall" actually mean?
- Each stone drops straight down as one rigid piece, keeping its shape, until it rests on the floor or on another stone. Stones do not tip, rotate or break apart, and one stone can come to rest on top of another. If a stone lands bridging a gap, the hole underneath stays empty — which is exactly what the rule forbids.
- Can a stone be a single cell?
- Yes. A one-cell room must hold a one-cell stone, and larger rooms can hold small stones too, as long as the drop still works out.
- Is there always exactly one answer?
- Yes. Every puzzle here is proved by solver before it is banked, and only puzzles with a single answer are kept.
- Do I need an account?
- No. Nothing to sign up for, nothing to install. Your progress is kept in your own browser.