Cave Solver

Cave Solver — Step by Step

Click a square and type its number, then press Solve. Or play a generated puzzle and send it here with one click.

Cave Solver: rules, how to use it, tips

Shade the rock so the white squares form one connected cave, every rock joins the edge, and each number sees exactly that many cave squares.

Every square is cave (white) or rock (shaded).
All cave squares form one connected area.
Every rock square is joined to the edge of the grid through other rock squares.
Each number is a cave square that sees exactly that many cave squares across and down, itself included, until rock or the edge.

Choose the size and type the numbers (or press Sample).
Press Solve and step through: what numbers must see, one cave, and rock joined to the edge.

Must see. If a number can’t reach its total without looking one way, it must see at least some squares that way.
Seen enough. Once a number sees its total, the next square in each direction is rock.
One cave. A square whose rock would split the cave must be cave.
Rock to the edge. A rock square boxed in by cave can’t be — follow the rock to the edge.

The full guide, with a worked example and common mistakes: How to play Cave.

Do rocks have to touch each other?

Each rock has to join the edge — through other rock squares or by touching the edge itself — but different rock areas don’t have to meet.

Does a number count itself?

Yes — a 1 sees only itself, so all four of its neighbours are rock.

Is there always one answer?

Yes — every puzzle here is checked to have exactly one solution.

How do I solve one from a book?

Open the Cave Solver, type the numbers and press Solve.