This scatter plot visualizes sleep efficiency against age, with each circle colored by deep sleep stage and sized to reflect sleep duration and REM sleep percentage. It uses D3 v6’s `csv` loader to parse the sleep-efficiency dataset, `scaleLinear` for both axes, and `axisLeft`/`axisBottom` for tick marks. The SVG is rendered full-window with static circle markers, colored via a hardcoded switch on species-like values, and manually rotated axis labels styled with inline fonts.