{
  "flagBits": {
    "0x0001": "passage down (bit 0)",
    "0x0002": "passage left (bit 1)",
    "0x0004": "passage right (bit 2)",
    "0x0008": "passage up (bit 3)",
    "0x000F": "all 4 passage directions",
    "0x0010": "higher tile / star flag (render above characters)",
    "0x0020": "ladder flag",
    "0x0040": "bush flag (semi-transparent overlay)",
    "0x0080": "counter flag (table / talk over)",
    "0x0100": "damage floor flag",
    "0x0200": "boat passable",
    "0x0400": "ship passable",
    "0x0800": "airship land OK",
    "0xF000": "terrain tag (bits 12-15, value 0-15)"
  },
  "commonFlags": {
    "0": "passable in all directions (o)",
    "15": "impassable in all directions (x)",
    "16": "no effect on passage (star/higher tile)",
    "1536": "passable + star flag (B-E decorative overlay)",
    "1551": "impassable + star flag (B-E wall/pillar overlay)",
    "1552": "impassable + counter flag (tables, counters)"
  },
  "passageCheck": "checkPassage(x, y, bit): iterates layeredTiles top-to-bottom. If flag & 0x10 → skip (no effect). If flag & bit === 0 → passable (return true). If flag & bit === bit → impassable (return false).",
  "terrainTag": "flags[tileId] >> 12 (bits 12-15, 0-15)",
  "regionId": "tileId at layer 5 of map data"
}