Panel

The color family the highlight active state paints in (`activeEmphasis="highlight"`), independent of `tone` — e.g. a primary current row in a neutral list. Ignored at other levels.

Surface background from the Panel scale (`surface.peak` → `surface.ground`, or `transparent`).

Border color at rest: `none`, `default`, `bold`, `muted`, or `accent`. The 1px line is always reserved when a border can appear, so changing it never shifts layout.

Border color while the surface is `active` — the explicit form of the ring `activeEmphasis` would otherwise pick. It holds through hover, so a `borderInteract` color can't steal it. `inherit` keeps whatever `activeEmphasis` chose; `none` clears it.

Border color on hover and press: `none`, `default`, `bold`, `muted`, or `accent`. Composes with `border`, e.g. a muted line at rest that turns bold on hover.

Which surface ramp the panel paints with: `primary` is the filled tone accent (with contrast text), `secondary` the tone's own surface tint, `tertiary` the neutral ramp with tone-accent text. `background` then picks the step on that ramp.

What hover and press paint on an interactive surface: `surface` steps the resting surface ramp; `highlight` paints the tone's highlight (`neutral.highlight` on a neutral surface) and its next step while pressed. An active surface keeps its own hover steps.

Elevation shadow applied to the surface.

Color tone: a semantic tone (`neutral`, `primary`, `success`, `warning`, `danger`, `inherit`) or a color family such as `teal`. A family carries no status meaning.

Frosted glass: the chosen `background` step at /35 with a large backdrop blur, so content behind the panel shows through. A transparent background stays transparent.

Inner padding from the spacing scale.

Corner radius from the radii scale (`full` for fully rounded). `inner` computes a concentric corner from the parent panel's radius minus its padding; `inherit` mirrors the parent's corner exactly, for a child that sits flush with its edge.

Corner radius for the bottom-left and bottom-right corners.

Corner radius for the top-left and bottom-left corners.

Corner radius for the top-right and bottom-right corners.

Corner radius for the top-left and top-right corners.

Keep (or drop) the always-1px transparent border the panel reserves so a border appearing or changing never shifts layout. Computed automatically — it's reserved when a resting `border` is visible, or when `interactive` / `borderInteract` / `active` can change the border at runtime. Set `false` only on a panel that must not occupy that 1px (e.g. a borderless housing frame that would otherwise add 2px around a set).

Opt this panel into the baseline rhythm: bakes `data-rhythm` on the root, so the whole subtree becomes a rhythm scope. The panel's padding turns into whole raster lines (minus its border) and text inside can quantise its own leading through the preset's `rhythm` pattern. A `<Grid rhythm>` (or any `[data-rhythm]`) ancestor makes the subtree rhythmic without this prop — the prop is how a panel opts ITSELF in, and how it takes the line-based padding.

Mark this as the chosen one in a set (a current nav item, a checked option, a selected card). Where `interactive` says it *can* be clicked, `active` says it *is* the current choice. Use `activeEmphasis` to control how loud the state is. Combined with `interactive`, hover and press restart their stepping from the active baseline rather than falling back to the unchosen ramp. The four values differ only in what drives the state: `true` by the prop (via `data-panel-active`), `"checked"` by a wrapped native input (`:has(input:checked)` — zero JS, nothing to re-render), `"current"` by an existing `aria-current` on the panel, and `"current-within"` by an `aria-current` on a direct child (a split nav row whose link carries it).

How loud the `active` state is. Defaults to the panel's own `emphasis`, so the chosen state lands on the same ramp as the resting look — this prop is the override for when the active item should be louder (or quieter) than the panel itself. `"primary"` fills with the tone accent ramp and flips text to the contrast scale (~150 RGB units of separation — the option that reads at a glance in a dense list). `"secondary"` tints the tone surface ramp and `"tertiary"` the neutral ramp; both promote text to `bold` and lift the border to the default line, but move the surface only ~7–18 units.

HTML element to render. Curated to container-like tags so semantic intent stays clear (no html/script/style/etc).

Enable interactive (hover / focus / press) affordances and states.

Serialize the panel's resolved surface inputs into a `data-panel-config` attribute on the root, enabling runtime surface changes via `updatePanelElement()` (and, for inheritors like Card, `updateCard()`) without a framework runtime — the primary consumer is Astro / vanilla JS, where props don't re-render. Reactive frameworks (Svelte/React/Vue) don't need this: their prop changes re-run the connect already.

The panel body content.

User-supplied `class` string. Appended last via `cx()`.

Extra data attributes to emit on the root (e.g. `{ shape: "circle" }` → `data-shape="circle"`). Values of `undefined`, `null`, or `false` are skipped.

Override the default `data-component="panel"` attribute.

Bindable reference to the rendered element. Typed loosely as `Element` to stay compatible with `svelte:element`'s union return type.

Static HTML/data attrs produced by an inheriting component. Spread before the consumer's `restProps` and `passThrough.root.props`, so both can override them.

Styles produced by an inheriting component (e.g. `cardStyles.raw().root`). Merged into the panel root's class between the recipe and the consumer's `passThrough.root.style`, so consumer overrides still win. Inheritors use this instead of funneling their slot styles through `passThrough.root.style` manually.

Per-slot style and attribute override bag for customizing the panel's elements.