Human2Human Chess Duell

Human2Human Chess Duell provides a complete online chess game for two human players.
There is no AI – only the full chess rules.

Features:

• Human vs human via a shared link (hash in the URL: ?chess_game=…)
• Whoever creates the game plays White; the second visitor automatically becomes Black.
  Further visitors watch the game as spectators.
• Players can choose their own name. For logged-in WordPress users the display
  name is pre-filled (and can be overridden).
• Logged-in WordPress users (any role) may bypass the limit of simultaneous games.
• Full chess rules: castling, en passant, pawn promotion,
  check/checkmate/stalemate, fifty-move rule, insufficient material.
• Server-side rule validation: every move is validated on the server
  (custom PHP engine). Cheating via a manipulated browser is not possible.
• Configurable in the backend: number of simultaneous games and the lifetime
  until automatic end (Settings > Human2Human Chess Duell).
• A game ends only by checkmate, resignation or draw – or expires after the
  configured period of inactivity (default 14 days).
• Optional chess clock when creating the game. Only the online time of the
  player to move is counted – if someone is offline, their clock pauses (no time
  spent overnight). On timeout the player loses.
• Optional e-mail notification when it is your turn (pre-filled for logged-in
  users with a stored address). The address is used only for the notification
  and automatically deleted when the game ends – not stored permanently
  (technically visible in the server log).
• Updates do not interrupt running games (backward-compatible data).
• Synchronization via the WordPress REST API (polling, every 2 seconds).
• No external dependencies (no CDN, no images) – Unicode chess pieces.
• In-game private chat between the two players, a move list, an optional
  “show piece names” tooltip helper, and a personal “continue on another
  device” link (e.g. move from desktop to phone).

The plugin interface is in English and fully translatable. A complete German
translation (de_DE, incl. de_DE_formal) is bundled with the plugin.