The open-source theme layer over Radix Primitives: 12-step color scales (indigo accent + slate gray by default) where each step has a defined job, automatic light/dark fidelity, translucent panels, a 9-size type scale on a system font stack, and accessibility inherited from headless primitives — the quiet, engineered look behind much of the modern React ecosystem.
Primary actionThe 12-step scale contract: step 1 app background, 3 hovered component, 6 borders, 9 solid accent, 11 low-contrast text, 12 high-contrast text — a palette API so predictable that dark mode is just swapping scales.