{
  "content": {
    "background_source": "local",
    "backgrounds_dir": "backgrounds/train",
    "background_fallback_url": "https://picsum.photos/seed/{seed}/{w}/{h}"
  },
  "render": {
    "puzzle_size": [400, 200],
    "piece_size_range": [50, 50],
    "knob_radius": 8,
    "tolerance_px": 10,
    "track_height": 44,
    "edge_margin": 10,
    "left_start_offset": 50,
    "aa_scale": 4
  }
}