This heat map visualizes a sequential color scale transitioning from purple to orange across a continuous spectrum. The view fills the browser window with 100 vertical rectangular bands, each colored via the `d3.scaleSequential` interpolator. The code uses `d3.interpolate` to blend the two colors, `d3.scaleLinear` for positioning, and SVG `<rect>` elements rendered with D3 v7. The example demonstrates how to construct a full-viewport gradient bar for quantitative data mapping.