Battleship
Two hidden fleets and a hundred squares each. The old objection to playing it with a stranger is that you cannot see their grid; here the fleet is sealed before the first shot and published at the end, so it can be checked.
The rules
- Each player has a grid ten squares by ten, and the same five ships: a carrier of five cells, a battleship of four, a cruiser and a submarine of three each, and a destroyer of two.
- Place every ship horizontally or vertically. Ships may not overlap or hang off the grid.
- That is seventeen cells of ship in all, which is the number that decides the game.
- Take turns calling one square on your opponent's grid. You are told at once whether it is a hit or a miss.
- When the last cell of a ship is hit, the ship is announced as sunk and named.
- The first player to hit all seventeen of the other fleet's cells wins.
Both fleets are sealed with a hash before the first shot and published when the game ends, so anyone can confirm that no ship moved after the shooting started. That is the one thing you cannot check when playing on paper with somebody you do not know.