A responsive area chart reveals a pink-filled curve and its stroke line from behind a sliding rectangular mask. Built with Svelte and D3, the visualization maps a fixed dataset of x and y values using `scaleLinear` and renders smooth paths via `line` and `area` generators with a Catmull-Rom curve. A CSS animation slides the overlay rect across the SVG, progressively unveiling the chart. The visualization demonstrates reactive sizing through Svelte's `bind:clientWidth` and `bind:clientHeight`.