Sea battle
Hide your fleet, hunt down the computer’s — one shot at a time.
Place your ships: pick one, then tap a square. Drag a ship to move it; press R or Rotate to turn it.
Your fleet
0 of 5 ships placed
Your record · NormalWins: 0Losses: 0Fewest shots to win: –
Your wins, losses and best game for each level are kept in this browser only.
Nothing leaves your device
This tool runs entirely in your browser. What you type, play or record here stays on your device: nothing is uploaded or saved on a server.
Example
Why the Hard computer opens on E5 or F6, and where it fires after a hit
Hard never sees your fleet. For every square it counts how many ways the ships still afloat (5, 4, 3, 3 and 2 squares long) could lie across it, given the shots so far, and fires at the highest count. On an empty grid the counts are:
- While hunting, Hard fires only at one colour of a chessboard pattern, 50 of the 100 squares, as even the 2-square ship must cross one. Of those, E5 and F6 count 34, so it fires first at one of them.
- After a hit on E5, ways that run through the hit count 200 times as much, so it fires next at F5 or E6 (2,422 each) rather than D5 or E4 (2,421).
- Normal fires at random until it hits, then tries the squares beside the hit and follows two hits in a line to the open ends. Easy fires at random all game.
- Your accuracy after a game is hits ÷ shots. A win always takes exactly 17 hits, so winning in 42 shots shows 40%.
| Square | Ways the five ships can cover it |
|---|---|
| A1, a corner | 10 |
| B1 | 15 |
| E1, middle of an edge | 22 |
| C3 | 28 |
| D4 | 32 |
| E5, F5, E6, F6, the centre | 34 |
Against Hard, ships along the edges and in the corners sit on the lowest counts, so it tends to reach them last; ships in the middle are found first. Against Easy, where you put them makes no difference.
How it works
- Place your five ships on your grid, or press Shuffle; then press Start battle.
- Fire at the enemy grid one square at a time: a hit, a miss or a ship sunk is marked.
- The computer fires back after each shot — sink all its ships before it sinks yours.
Frequently asked questions
- What are the rules?
- Each side hides five ships — 5, 4, 3, 3 and 2 squares long — on a 10 × 10 grid, across or down. Players take turns naming a square to fire at; the other says hit, miss or sunk. The first to sink the whole enemy fleet wins.
- How strong is the computer?
- Easy fires at random. Normal hunts around every hit and follows the line of a ship. Hard aims where ships are most likely to be, given the squares already fired at and the ships still afloat. It never sees your fleet.
- Can ships touch?
- Yes — ships may lie side by side, but not overlap. Bunching them is not always wise: against Normal, which hunts round every hit, a fleet packed into one corner goes down about 20 shots sooner than a spread-out one; against Hard, which starts in the middle, the same corner holds out about 15 shots longer.
- Can I play with a friend?
- This page is against the computer. To play with a friend on paper, print sheets with the printable game sheet maker.
- Where should I place my ships?
- Against Hard, towards the edges: it aims where the most possible ship positions overlap, and a corner square can be covered in 10 ways against 34 in the centre. Against Easy it makes no difference, and Normal only hunts around its hits.
- How is accuracy worked out?
- Hits divided by shots, rounded to a whole percent. Sinking a fleet takes 17 hits, so a win in 42 shots is 40%. Your record also keeps the fewest shots you needed to win at each level.
- Is anything sent anywhere?
- No. The game runs in your browser and your record stays on this device.
Related tools
♟ PDF tools Sea battle printable Two grids, a fleet and a pencil. ♞ Chess A full game of chess against the computer or a friend — no account needed. ✹ Minesweeper Clear the field without touching a mine — the numbers tell you where they are. # Tic-tac-toe Three in a row wins — can you beat the unbeatable level?