The left sidebar can be adjusted from config.toml: width, background color, border, and item spacing.
[extra]
nav_width = "18%"
nav_bg = "#f0f0ff"
nav_border = true
nav_item_gap = "1.3em"The defaults follow Hiroshi Abe's homepage: a pale lavender background and an 18% sidebar.
On narrow screens, the sidebar automatically becomes a top horizontal menu.