A basic donut chart with the total/aggregate value shown in the center of the donut. Much of the formatting (font size, spacing, etc.) is customizable by the user in the config options.
This chart is a good starting place for any other custom donut or pie chart visualizations, since Looker does not make the source code for their native visualizations available.
This visualization uses the Chart.js data visualization library for the donut chart.
https://www.chartjs.org/docs/latest/charts/doughnut.html
