Donut Chart (Vega-Lite)

{
  "$schema": "https://vega.github.io/schema/vega-lite/v5.json",
  "title": "Pie Chart",
  "width": 200,
  "height": 200,
  "data": {
    "values": [
      {"category": "A", "value": 28},
      {"category": "B", "value": 55},
      {"category": "C", "value": 43},
      {"category": "D", "value": 34}
    ]
  },
  "mark": {"type": "arc", "innerRadius": 40},
  "encoding": {
    "theta": {"field": "value", "type": "quantitative"},
    "color": {"field": "category", "type": "nominal"}
  }
}