This example shows a simple bar chart of 20 numeric values using D3. It renders an SVG with rectangles and text labels, where bar height and color intensity map to each data point. The code uses `d3.select` to build the SVG, `.data()` with `.enter()` to bind the dataset, and `.append('rect')` and `.append('text')` to draw the visualization. Bars are positioned with computed `x`, `y`, and `height` attributes, while labels display the values in white sans-serif text.