...It ships a catalog of popular dark and light themes and lets you customize fonts, font sizes, cell widths, and toolbar visibility so the notebook matches your preferred reading and coding ergonomics. The theming system adjusts CodeMirror syntax highlighting to keep code legible against chosen backgrounds and provides options to harmonize matplotlib/plotly colors for cohesive visuals. Installation and usage are streamlined through a single jt command, with flags to set or preview themes and a built-in restore option to return to defaults. Because it modifies the Notebook’s CSS, the project focuses on lightweight overrides rather than invasive changes, minimizing breakage across notebook versions. ...