rabbit-theme-sumi

Sumi-ink dark theme for Rabbit: grayscale palette, text item marks, no frames. Everything except syntax highlighting is built from hueless shades of gray. Emphasis is expressed with lightness, weight and italics instead of hue. Item marks are drawn as U+25AA (BLACK SMALL SQUARE) characters instead of images or shapes, and are the same at every level. Headline underlines and the frames around block quotes and code blocks are removed; those blocks are shown as rounded panels one step lighter than the background.