{
  "patternType": "PIN",
  "description": "Classical bishop pin on the Ruy Lopez diagonal, tying the c6-knight to the e8-king.",
  "cases": [
    {
      "id": "pin_ruy_lopez_knight_to_king",
      "initialFen": "r1bqkbnr/pppp1ppp/2n5/4p3/4P3/5N2/PPPP1PPP/RNBQKB1R w KQkq - 2 3",
      "sideToMove": "white",
      "bestMove": { "san": "Bb5", "uci": "f1b5" },
      "resultingFen": "r1bqkbnr/pppp1ppp/2n5/1B2p3/4P3/5N2/PPPP1PPP/RNBQK2R b KQkq - 3 3",
      "expectedPattern": {
        "type": "PIN",
        "side": "white",
        "attackerSquares": ["b5"],
        "targetSquares": ["c6"],
        "keySquares": ["e8"],
        "explanationKey": "pin_to_king"
      },
      "context": "1.e4 e5 2.Nf3 Nc6 3.Bb5 with the knight pinned to the king.",
      "tags": ["opening", "ruy_lopez"]
    }
  ]
}