This example demonstrates brushing on a scatterplot of borehole data, plotting depth against time. Users drag a horizontal brush across the chart to zoom the x-axis into a selected date range, with circles and the axis smoothly transitioning over one second. The visualization uses D3 v4 APIs including `d3.brushX`, `d3.scaleLinear`, `d3.axisBottom`, and `d3.transition` to update the view, while the data is loaded as CSV from an external URL. SVG rendering animates the filtered result.