{
  "$schema": "https://vega.github.io/schema/vega-lite/v5.8.0.json",
  "config": {"view": {"continuousHeight": 300, "continuousWidth": 300}},
  "datasets": {"empty": [{}]},
  "height": 600,
  "layer": [
    {
      "data": {
        "name": "tile_list",
        "sequence": {"as": "a", "start": 0, "stop": 4}
      },
      "encoding": {
        "url": {"field": "url", "type": "nominal"},
        "x": {"field": "x", "scale": null, "type": "quantitative"},
        "y": {"field": "y", "scale": null, "type": "quantitative"}
      },
      "mark": {
        "clip": true,
        "height": {"expr": "tile_size - 10"},
        "type": "image",
        "width": {"expr": "tile_size - 10"}
      },
      "projection": {
        "center": [0, 50],
        "rotate": [-10, 0, 0],
        "scale": 400,
        "type": "mercator"
      },
      "transform": [
        {"as": "b", "calculate": "sequence(0, 4)"},
        {"flatten": ["b"]},
        {
          "as": "url",
          "calculate": "'https://tile.openstreetmap.org/' + zoom_ceil + '/' + ((datum.a + dii_floor + tiles_count) % tiles_count) + '/' + (datum.b + djj_floor) + '.png'"
        },
        {"as": "x", "calculate": "datum.a * tile_size + dx + (tile_size / 2)"},
        {"as": "y", "calculate": "datum.b * tile_size + dy + (tile_size / 2)"},
        {
          "filter": "((datum.a + dii_floor + tiles_count) % tiles_count) >= 0 && (datum.b + djj_floor) >= 0 && ((datum.a + dii_floor + tiles_count) % tiles_count) <= (tiles_count - 1) && (datum.b + djj_floor) <= (tiles_count - 1)"
        },
        {
          "filter": "datum.x < (width + tile_size / 2) && datum.y < (height + tile_size / 2)"
        }
      ]
    },
    {
      "data": {
        "format": {"feature": "countries", "type": "topojson"},
        "url": "https://cdn.jsdelivr.net/npm/vega-datasets@v1.29.0/data/world-110m.json"
      },
      "encoding": {
        "fill": {"field": "id", "legend": null, "type": "quantitative"}
      },
      "mark": {
        "fillOpacity": 0.1,
        "stroke": "orange",
        "strokeWidth": 2,
        "type": "geoshape"
      },
      "projection": {
        "center": [0, 50],
        "rotate": [-10, 0, 0],
        "scale": 400,
        "type": "mercator"
      }
    },
    {
      "data": {"name": "empty"},
      "encoding": {"x": {"value": 0}, "y": {"value": {"expr": "height"}}},
      "mark": {
        "align": "left",
        "dx": 3,
        "dy": -8,
        "text": "(C) OpenStreetMap contributors",
        "type": "text"
      }
    }
  ],
  "params": [
    {
      "expr": "(2 * PI * pr_scale) / pow(2, zoom_level)",
      "name": "base_tile_size"
    },
    {"expr": "400", "name": "pr_scale"},
    {"name": "zoom_level", "value": 1},
    {"expr": "ceil(zoom_level)", "name": "zoom_ceil"},
    {"expr": "pow(2, zoom_ceil)", "name": "tiles_count"},
    {
      "expr": "base_tile_size * pow(2, zoom_level - zoom_ceil)",
      "name": "tile_size"
    },
    {"expr": "invert('projection', [0, 0])", "name": "base_point"},
    {"expr": "(base_point[0] + 180) / 360 * tiles_count", "name": "dii"},
    {"expr": "floor(dii)", "name": "dii_floor"},
    {"expr": "(dii_floor - dii) * tile_size", "name": "dx"},
    {
      "expr": "(1 - log(tan(base_point[1] * PI / 180) + 1 / cos(base_point[1] * PI / 180)) / PI) / 2 * tiles_count",
      "name": "djj"
    },
    {"expr": "floor(djj)", "name": "djj_floor"},
    {"expr": "round((djj_floor - djj) * tile_size)", "name": "dy"}
  ],
  "width": 600
}