Battleship

• Placement
• Numbers
• Regions

Locate the complete hidden fleet using row, column and revealed-cell clues.

1. Place exactly the indicated fleet; every ship is a straight horizontal or vertical line.
2. Ships may not touch each other, not even diagonally.
3. Each row or column number tells how many cells in that line contain ship segments.
4. Ship or water cells revealed at the start are fixed clues and cannot be changed.
5. Tap a cell to cycle through empty, ship and water; right-click or use Shift + Space to cycle backwards.

• Mark water in zero-count rows and around confirmed ships; this restricts both positions and remaining ship lengths.
• Start with rows and columns marked 0: every cell in them is water.
• When a line already contains all its required ship segments, mark the remaining cells as water.
• Every ship segment forces its diagonal neighbours to be water because ships cannot touch at corners.
• Keep the remaining fleet in mind: longer ships need enough straight space.

We do not yet have a sufficiently verified account of this game’s origins. Rather than guess, we avoid attributing a date or creator without reliable evidence.

• Start with rows and columns marked 0: every cell in them is water.
• When a line already contains all its required ship segments, mark the remaining cells as water.
• Every ship segment forces its diagonal neighbours to be water because ships cannot touch at corners.
• Keep the remaining fleet in mind: longer ships need enough straight space.

• Where should I begin? Mark water in zero-count rows and around confirmed ships; this restricts both positions and remaining ship lengths.
• What makes this game different? Tap a cell to cycle through empty, ship and water; right-click or use Shift + Space to cycle backwards.