Boats

You’re given a grid, and a list of boats which must be located inside that grid. Boats can be rotated. Two boats cannot be horizontally, vertically or diagonally adjacent.

The numbers on the side indicate the amount of cells inside that row or column which are occupied by a boat.

Some boat segments are given (corner pieces, centers, or single-length boats), along with their orientation. A given segment sits on a lighter square, and cannot be changed.

Controls

On a touch screen, a tap does what a click does, and a long press what a right-click does (more ways to right-click).

Click a square to cycle it from empty to a boat segment, then water, then empty again. Right-click it to place water, to say no boat can go there, or empty it if it is filled.

With the keyboard, the arrow keys move a cursor around the board. Enter does what a click does to the square under it, and Space what a right-click does. Press Backspace or Delete to empty it; clicking it round gets there too.

Unknown boat segments are represented by a small rectangle, and will automatically change into the correct shape when the surrounding cells are filled in.

Drag along a row or column to fill every square it passes over the way the first one changed. A drag that turns its first square to water does so to every square it passes that is not given, whatever each one held. Hold Ctrl while moving the cursor to place boat segments on the empty squares it passes over, Shift to place water, or both to empty them.

The list of boats

At the bottom of the puzzle is a list of every boat that must be placed in the grid. When a boat is found, it is automatically crossed off of this list. Make sure a boat is surrounded by water on all sides, to indicate that it cannot possibly grow any further.

Where the puzzle comes from

This puzzle is best known as Battleships.

More information: https://www.janko.at/Raetsel/Battleships/index.htm

Hints

Hint explains the next step rather than simply making it. It reasons from the numbers, the given segments and the boat segments and water you have placed, so it carries on from wherever you are, as long as none of them is wrong; if one is, it asks you to fix the highlighted mistakes first.

• A ring marks the squares the step decides, drawn in the hint color in the shape of what goes there: a small boat segment for a boat square, two wavy lines, like a given water square’s, for water. A step that places a boat segment also shows the water that has to go round it.
• An outline marks the squares it reasons from, such as a given segment, the rest of an unfinished boat, or the water that closes a square in.
• Stripes mark the row or column whose number it counts with, and the stripes run on through that number.

Boats never touch, not even at a corner, so a step that places a boat segment also shows the water that has to go round it. That water is part of the same step, and the sentence names it without saying why each time. A free square, in the hint’s words, is one still empty: neither a boat segment nor water. A run is a stretch of free squares in a row or column that a boat could lie along.

With Remove numbers on, some rows and columns have no number. When a step needs one anyway, it first says what that hidden number can only be.

A few ideas are worth learning by name:

• A given end shows its boat’s direction. A boat’s top end must continue downward and have water above it; a middle segment runs through, one way or the other.
• A full row is finished. Once a row has as many boat segments as its number, everything else in it is water; once its free squares are exactly as many as it still needs, they are all boat segments.
• The fleet list counts too. When every boat of some size is already placed, a square that would make another one, or make a boat longer than the largest still missing, must be water. And an unfinished boat that has reached that size can’t stop there: it must continue into the next square.
• On harder boards, if this square were its row’s last water: where a row or column needs exactly one more water or boat square, the hint tries a square as that last one, the rest of the line the other, and shows which rule that would break, such as a column that could no longer reach its number.

Boats parameters

These parameters are available from the ‘Custom type…’ option on the ‘Type’ menu.

Width, Height

Size of the grid in squares. Each must be between 2 and 99.

Fleet size

The size of the largest possible boat. It cannot be larger than both the width and the height. It must be between 1 and 9.

Fleet configuration

Customize the fleet by entering a list of numbers. Each number indicates how many times a boat of a specific size appears. For example, the configuration 3,2,1 represents 3 boats of size 1, 2 boats of size 2, and 1 boat of size 3. A fleet of one boat has only Easy puzzles.

Difficulty

Determine the difficulty of the generated puzzle; see what the names mean.

Remove numbers

When enabled, the difficulty is increased by hiding certain number clues.

More help

• Features every puzzle shares: hints, checking your work, checkpoints, playing by touch
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