In our UI system we dont use pixel values to define spacing, we use semantic variables, (t-shirt sizes: gap-sm , p-lg , my-2xl ) - so thats like you change one CSS variable, and the whole UI adapts. We limit user customization to just 5 presets - 0.8 / 0.9 / 1 / 1.1 / 1.2 : Symmetric around 1.0 - two steps down, two up; ±20% is deliberately restrained  - enough to change the feel (data-dense ↔ spacious) without breaking layouts or distorting prop...