What Is a Cave Puzzle? Rules and Solving Tips

What is a Cave puzzle?

What is a Cave puzzle in practice? You start with a grid that holds a scattering of numbers, and you decide which cells to shade as solid wall and which to leave open as the cave. The open cells form one continuous cavern, while the shaded wall cells press in from the outside. This puzzle is also known as Corral or Bag, and its charm is the way sight lines do the talking: each number is standing in the cave looking down four hallways, and it tells you the total length of what it can see. Nothing is arithmetic here; a Cave puzzle is all about visibility and connection, and the outline of the cavern slowly emerges as you honour each clue.

The rules of a Cave puzzle

• Shade some cells as wall and leave the rest as the cave; every numbered cell stays part of the cave.
• All cave cells form one single connected area, joined edge to edge.
• Every wall cell connects to the outside border of the grid through other wall cells, so no wall is fully sealed inside the cave.
• A number counts the cave cells it can see in a straight line up, down, left and right, including its own cell, stopping wherever a wall blocks the view.
• The count runs in all four directions from the clue and adds up to the printed number exactly.

Imagine a clue showing the number 1. A cell that sees only itself must be boxed in on all four sides by wall cells or by the grid edge, because any open neighbour would raise its count. Now take a clue showing 6 sitting in the middle of a row. It might see itself, two open cells to the left before a wall, and three open cells upward before the ceiling closes in, for a total of six. If you already know a wall sits two cells to its right, then the remaining cells it can see are pinned down, and the shape of that corridor becomes fixed. Each clue you resolve tightens the outline of the cavern until only one legal cave remains.

Beginner tactics for Cave puzzles

1. Start with the 1s. A clue of 1 must be completely surrounded by wall, which hands you four shaded cells at once.
2. Let big numbers open long corridors. A large clue needs plenty of unbroken cave in a line, so those cells cannot be walls.
3. Keep the cave in one piece. If shading a cell would split the open area into two separate caverns, that cell must stay open.
4. Make sure walls can escape to the edge. A shaded cell trapped in the middle with no wall route to the border breaks the rules, so reconsider it.
5. Overlap two clues. Where the sight lines of two numbers cross, the combined constraints often reveal a single legal arrangement.

How a Cave puzzle compares to Sudoku

Sudoku fills every cell with a digit under strict row, column and box rules; a Cave puzzle instead asks you to paint the board into two zones and reason about connection and line of sight. The numbers in a Cave puzzle behave nothing like Sudoku digits, since a 6 is not a value to place but a measurement to satisfy. Yet both puzzles reward the same disciplined habit: make only the moves that logic forces, and let each certainty unlock the next. If you enjoy that quiet, no-guessing style, Shapedoku offers the classic Sudoku experience with nine glowing shapes in place of the numbers, so colour and form guide your deductions. It is free to play at app.shapedoku.com, and shapedoku.com has a solver and printable puzzles whenever you want to switch off the screen and solve on paper.