This example shows a brushable line chart for exploring genomic coverage data, plotting the percentage of covered positions along a chromosome. The main focus panel displays multiple colored lines, while a smaller context panel below provides a zoomed-out overview. Using D3.js v5, the visualization employs `d3.brushX` to allow brushing on the context chart, which updates the x-axis domain of the focus panel via a brush event handler. Data is loaded from a CSV file with `d3.csv`, and lines are rendered as SVG paths using `d3.line` with scales from `d3.scaleLinear`.