This visualization displays the moon’s phase for each day of 2021, arranged as a calendar grid with months on the vertical axis and days on the horizontal axis. Each moon is rendered via `d3.geoPath` and `d3.geoOrthographic` with circles and paths showing the illuminated portion based on a simplified lunar phase calculation from ben-daglish.net. Clicking anywhere on the SVG animates a red ring to highlight the current day using a `transition` with duration and stroke attributes, while axes are built with `d3.axisTop` and `d3.axisBottom`.