[
  {
    "id": "closed-rectangle",
    "width_mm": 40,
    "height_mm": 20,
    "paths": [
      "M 0 0 L 40 0 L 40 20 L 0 20 Z"
    ],
    "purpose": "One closed path, no transforms"
  },
  {
    "id": "circular-corners",
    "width_mm": 40,
    "height_mm": 20,
    "paths": [
      "M 4 0 L 36 0 A 4 4 0 0 1 40 4 L 40 16 A 4 4 0 0 1 36 20 L 4 20 A 4 4 0 0 1 0 16 L 0 4 A 4 4 0 0 1 4 0 Z"
    ],
    "purpose": "Four genuine circular corner arcs, no tessellation"
  },
  {
    "id": "two-path-overlap",
    "width_mm": 40,
    "height_mm": 20,
    "paths": [
      "M 0 0 L 40 0 L 40 20 L 0 20 Z",
      "M 0 0 L 40 0"
    ],
    "purpose": "Closed rectangle plus intentionally open path overlapping its top edge"
  }
]