{
  "schemaVersion": "legen-sudoku-published-catalog-report/v1",
  "reportMonth": "2026-07",
  "period": {
    "start": "2026-07-17",
    "end": "2026-07-31",
    "dates": 15,
    "puzzles": 60
  },
  "source": {
    "schemaVersion": "legen-sudoku-daily-catalog/v1",
    "releaseCutoff": "2026-08-15",
    "rawSha256": "c74d7ff54917d88a00cddd452b05764149f9a1baefc856e79a7e65d4576fbb26",
    "canonical": "https://sudoku.legen.uk/sudoku-data"
  },
  "engineVersion": "legen-sudoku-engine/1.3.0",
  "ldiVersion": "legen-ldi/v0/sha256:f541ca7389fce1f8257d6051209f234ddcd83980c1834ea29c078e6af58e0dd7",
  "tierCounts": {
    "easy": 15,
    "expert": 15,
    "hard": 15,
    "medium": 15
  },
  "difficultyIndex": {
    "overall": {
      "min": 0,
      "median": 21.5,
      "max": 95
    },
    "byTier": {
      "easy": {
        "min": 0,
        "median": 9,
        "max": 14
      },
      "medium": {
        "min": 15,
        "median": 19,
        "max": 21
      },
      "hard": {
        "min": 22,
        "median": 24,
        "max": 35
      },
      "expert": {
        "min": 39,
        "median": 68,
        "max": 95
      }
    }
  },
  "logicalSteps": {
    "overall": {
      "min": 49,
      "median": 55,
      "max": 65
    },
    "byTier": {
      "easy": {
        "min": 49,
        "median": 53,
        "max": 57
      },
      "medium": {
        "min": 51,
        "median": 53,
        "max": 57
      },
      "hard": {
        "min": 53,
        "median": 55,
        "max": 58
      },
      "expert": {
        "min": 53,
        "median": 62,
        "max": 65
      }
    }
  },
  "hardestTechniqueCounts": {
    "hidden-pair": 5,
    "hidden-single": 37,
    "locked-candidates": 6,
    "naked-pair": 2,
    "naked-single": 3,
    "xy-wing": 7
  },
  "highestObservedTechnique": "xy-wing",
  "hardestPuzzles": [
    {
      "date": "2026-07-18",
      "difficulty": "expert",
      "puzzleId": "LDI0-0a49699ec02f55dac179fe08d81a5a32739ada01",
      "difficultyIndex": 95,
      "logicalStepCount": 65,
      "hardestTechnique": "xy-wing",
      "canonical": "https://sudoku.legen.uk/daily-sudoku/2026-07-18"
    },
    {
      "date": "2026-07-23",
      "difficulty": "expert",
      "puzzleId": "LDI0-17ab0fdee343d133f6081557667d6e21c105c133",
      "difficultyIndex": 87,
      "logicalStepCount": 62,
      "hardestTechnique": "xy-wing",
      "canonical": "https://sudoku.legen.uk/daily-sudoku/2026-07-23"
    },
    {
      "date": "2026-07-20",
      "difficulty": "expert",
      "puzzleId": "LDI0-1399d1cd52c5113e0b92f011f45986f36505cae7",
      "difficultyIndex": 85,
      "logicalStepCount": 63,
      "hardestTechnique": "xy-wing",
      "canonical": "https://sudoku.legen.uk/daily-sudoku/2026-07-20"
    },
    {
      "date": "2026-07-17",
      "difficulty": "expert",
      "puzzleId": "LDI0-07c296b8e4ff384332ad2017fd093e174b9e9ea3",
      "difficultyIndex": 75,
      "logicalStepCount": 65,
      "hardestTechnique": "hidden-pair",
      "canonical": "https://sudoku.legen.uk/daily-sudoku/2026-07-17"
    },
    {
      "date": "2026-07-22",
      "difficulty": "expert",
      "puzzleId": "LDI0-16fa737582509950ea3769f3ef1474f7fd505691",
      "difficultyIndex": 75,
      "logicalStepCount": 65,
      "hardestTechnique": "hidden-pair",
      "canonical": "https://sudoku.legen.uk/daily-sudoku/2026-07-22"
    }
  ],
  "limitations": [
    "The four difficulty tiers each contain exactly fifteen puzzles by publication design, so tier counts are not a natural population distribution.",
    "The period covers the published catalog batch from 2026-07-17 through 2026-07-31, not player activity or a full natural-month observation window.",
    "No completion-time, hint, error, region, account, or other player-behavior data is used.",
    "Results describe the fixed engine and LDI versions shown in this report."
  ],
  "canonical": "https://sudoku.legen.uk/sudoku-data/reports/2026-07"
}