Battleships Puzzle

Battleships is a shading puzzle. You find a hidden fleet. Every cell is ship or water, the ships stay straight and apart, and the numbers outside the grid all match. You can play grids from 6×6 up to 10×10, and every puzzle here has exactly one solution that you can reach by logic, with no guessing.

Rules

The board is an n×n grid. A number sits left of each row and above each column. That number is how many ship cells the line holds. Zero is printed, so a blank line is never a missing clue.

Each ship is a straight run of 1, 2, 3, or 4 cells, across or down. Ships never touch, even at a corner. The bars under the grid are the fleet: those lengths, and no others. A round mark is a one-cell ship. A triangle is an end, and it points toward the rest of the ship. A bar inside the grid is a middle segment. Those marks are given, and so are any extra ship or water cells printed in the grid. You cannot change them. When every cell is marked, the ships match the fleet, and every count is right, the puzzle is solved. Water is part of the answer, not a pencil note.

Controls

Click or tap an open cell to cycle empty, then ship, then water, then empty again. Shift-click, right-click, or a long-press cycles the other way. Drag across open cells to paint water. Segment marks and extra givens do not take a new mark. Selecting one only moves the cursor.

On a keyboard, the arrow keys move around the grid. S or 1 places a ship. W, X, M, period, or 2 marks water. Backspace, Delete, or 0 clears the cell. Space or Enter cycles forward. Shift with Space or Enter cycles backward.

A count turns teal when the ships on that line match it. It turns coral when the line has too many ships, or when the open cells cannot reach the count. Ships that touch, a bent run, and a fleet the marks cannot be turn coral while error highlighting is on. Press Hint for one mark the rules already force, with a sentence saying why. Undo and Redo step through your moves, and Reset clears every ship and every water mark you placed. When the grid is right, the board turns teal. The timer, Check, Print, and Download PDF sit with the other controls.

Tips

Start with the segment marks. A one-cell ship makes every neighbour water. An end grows one cell in the direction it points, and the cell behind it is water. A middle grows both ways along its bar. A count of 0 is all water. When a line already has its ships, the rest of that line is water. When a line still needs a ship in every open cell, fill those cells. The fleet tells you which lengths are still left, so a cell no remaining ship can use is water.