Battleship Game Engine

Design a two-player grid battleship engine. Ships occupy straight contiguous cells, cannot overlap and remain hidden from the opponent. Repeated shots are invalid and must not consume a turn.

The domain engine must enforce placement, turns and terminal rules while preserving hidden information. Analyse what each player's view is allowed to reveal, not just whether the renderer hides the opponent's board.

Begin with explicit placement/play/finished phases and private board ownership. Mutating cells during partial validation leaves illegal fleets. Commit a complete valid placement or shot transition and produce scoped public snapshots afterward.

1. Validate complete nonoverlapping fleets before play starts.
2. Enforce actor, phase and coordinate rules.
3. Track unique shots, hits, sunk ships and terminal victory.
4. Return player-scoped views without leaking hidden ship positions.

Validate fleet placement fully before committing a board, including shape, bounds and overlap. During play, a shot identity and turn transition commit together. Public views expose only permitted results; copying the opponent's full board and hiding it in the renderer still leaks secret state to callers.

A ship crossing the board edge is rejected without placing its valid prefix. A repeated shot cannot consume a second turn or register a second hit. When the last intact ship cell is hit, the game becomes terminal and the opponent view reveals only the information allowed by that terminal-state policy.