This example visualizes a single circular sector, or “eye,” using D3’s `d3.arc` generator. It shows an angular segment with an inner and outer radius, filled in light gray, while a separate path highlights the arc’s outline. The visualization is rendered as an SVG element with a fixed width of 1860 pixels and height of 1000 pixels, centered on the canvas. The code defines two radii and a start angle of 0 with an end angle of π/4, though the end angle uses `Math.pi` (a typo for `Math.PI`), which would result in a fraction of the full circle. The approach relies on D3 v4’s arc helper to compute the path data, demonstrating a simple geometric shape rather than data-driven mapping.