Where Rux differs from CSS
The short list of places Rux does not answer the way CSS does, and which kind of difference each one is.
The rule, set 2026-09-18: Rux's CSS behaves the way real CSS does, defaults included, unless a divergence is genuinely necessary. An author arrives knowing CSS, and every place Rux answers differently is something they learn by being surprised in the window. Documenting a divergence does not pay for it; only necessity does, and "better ergonomics" is not necessity.
So this list is short on purpose, and each entry says which kind it is.
| Difference | Kind | Standing |
|---|---|---|
Flex cross-axis defaults to flex-start, not stretch | a preference, taken for ergonomics | To be reverted. It changes the layout of every existing document, so it is scheduled rather than patched |
border-radius in percent resolves against the shorter side, so 50% on a 160x60 box is a pill and not CSS's ellipse | a capability: Rux draws one radius per corner and cannot draw an elliptical corner | Keep |
No inline text flow: two <text> siblings stack instead of sharing a line | a capability: the layout engine has no inline layout, which is why display: inline was built and then removed | Keep |
Two things that look like differences and are not: display defaults to
block, and flex: 1 means 1 1 0%. Both are CSS's own answers.