{
  "$schema": "urn:prism:schema:v1:spec",
  "title": "Top-oriented shared axis across layers",
  "layer": [
    {
      "$schema": "urn:prism:schema:v1:spec",
      "data": {"values": [
        {"week": "W1", "visits": 120},
        {"week": "W2", "visits": 180},
        {"week": "W3", "visits": 140},
        {"week": "W4", "visits": 210}
      ]},
      "mark": "bar",
      "encoding": {
        "x": {"field": "week", "type": "nominal", "axis": {"orient": "top"}},
        "y": {"field": "visits", "type": "quantitative"}
      }
    },
    {
      "$schema": "urn:prism:schema:v1:spec",
      "data": {"values": [
        {"week": "W1", "visits": 150},
        {"week": "W2", "visits": 150},
        {"week": "W3", "visits": 150},
        {"week": "W4", "visits": 150}
      ]},
      "mark": {"type": "rule", "stroke": "#dc2626", "stroke_dash": [4, 2]},
      "encoding": {
        "x": {"field": "week", "type": "nominal"},
        "y": {"field": "visits", "type": "quantitative"}
      }
    }
  ]
}