A multi-series chart compares average smartphone price and battery life by brand from a CSV dataset. White bars show average price against a left axis, while a neon sky-blue line and dots show average battery hours against a right axis. Built with React hooks and D3 v6, it uses `scaleBand`, `scaleLinear`, `axisLeft`, `axisRight`, and `d3.line` to render SVG elements. Brand labels rotate on the x-axis, and a legend appears below.