This example shows a monthly time series of twelve data points from a local dataset, with a single black polyline connecting values, labeled x-axis dates, and a large final-value annotation. It also adds light-gray circular markers that turn red on hover, displaying the current value and a dashed vertical guide line. Built with D3 v4, it uses `d3.scaleTime` for the date axis, `d3.scaleLinear` for values, `d3.line` to generate the path, and SVG elements rendered via the code. The dataset is loaded with `d3.json` from a static file, and all interaction logic resides in `mouseover` and `mouseout` event handlers.