# Radius Scale

## Objective

Fix the app's corner radii to a few steps that agree with one another.

A small radius scale mapped to component roles — controls, cards, overlays, pills, media — and applied throughout.

## Before You Begin

This feature is being added to an application that already exists and already
works. Do not scaffold a new project, and do not assume a blank slate.

Inspect the codebase first and establish:

- The existing application structure and where code of this kind already lives.
- The framework and version in use.
- The existing design system — colours, spacing, typography, and component conventions.
- Existing UI components you can reuse instead of writing new ones.
- The existing database structure, if this feature needs to persist anything.
- The existing authentication and authorization system, if this feature is user-scoped.
- Dependencies already installed, so you don't add a library that duplicates one.
- The existing test setup and conventions.

Only start writing code once you understand the above. If the application
already implements part of this feature, extend it rather than replacing it.

## Implementation Instructions

1. Collect every corner radius in the codebase and reduce it to three or four steps, then assign each step a role: controls and inputs, cards and panels, overlays and sheets, fully rounded pills.
2. Set nested radii so the inner corner is smaller than the outer one by roughly the padding between them. An inner element with the same radius as its container leaves a visible sliver of gap at each corner.
3. Scale the radius with the component: the step that reads as softly rounded on a small button reads as barely rounded on a large panel, and as a lozenge on a short chip.
4. Reserve the fully rounded step for shapes it suits — chips, tags, avatars, counters — and keep it off anything tall or wide enough for the curve to eat its content. Do not apply a pill radius to a multi-line container, where the ends bulge and the text no longer sits inside the shape.
5. The Spacing Scale entry owns the padding values; this entry owns the corners. Where a nested radius depends on padding, read the spacing token rather than restating the number here.

## UI and UX Requirements

Match the application's existing design system exactly. Reuse its components,
spacing, and typography. This feature should look like it was always there.

## Responsive Requirements

Works on mobile, tablet, and desktop. Touch targets are large enough to hit on a
phone, and nothing overflows horizontally at 320px.

## Accessibility Requirements

- Fully keyboard navigable.
- Correct semantic elements and ARIA roles.
- Visible focus states.
- Meets WCAG AA contrast.
- Dynamic changes are announced to screen readers.
- Respects prefers-reduced-motion.

## Edge Cases

- Nesting a rounded element inside another rounded element with the same value produces a mismatched corner and a visible gap. Derive the inner radius from the outer one and the padding between them.
- A fully rounded radius on a tall or multi-line element turns it into a lozenge with unusable corners. Restrict the pill step to elements whose height stays close to a single line.
- One radius across every size is wrong at both ends. Map larger components to larger steps so the curve stays proportionally the same rather than numerically the same.
- Clipping a container to round its corners will also clip focus rings, shadows, tooltips, and dropdowns that need to escape it. Round the media or the inner surface rather than the container that holds an overlay.
- A theme with zero radius must still work: nothing may depend on the curve to separate two surfaces, or the flat theme will read as a single undifferentiated block.
- Grouped controls — segmented buttons, split buttons, joined inputs, table corners — need per-corner radii so only the outer edges of the group are rounded.
- Circular avatars and pill shapes are different intentions that happen to share a value. Name them separately so changing one does not silently change the other.

## Testing

Exercise the feature end to end in the running application. Cover every edge case
above, then run the existing test suite and confirm nothing regressed.

## Acceptance Criteria

- [ ] The app uses three or four radius steps, each mapped to a documented component role.
- [ ] Nested elements use an inner radius derived from the outer radius and the intervening padding.
- [ ] Radius scales with component size rather than one value applied at every scale.
- [ ] The fully rounded step appears only on single-line or circular shapes.
- [ ] Focus rings, shadows, and overlays are not clipped by a rounded container.
- [ ] A zero-radius theme renders with every surface boundary still legible.
- [ ] Grouped controls round only the outer corners of the group.
- [ ] The feature matches the existing design system.
- [ ] No existing functionality is broken.

## Adaptation Rules

- Match the existing design system. Do not introduce a new colour palette,
  spacing scale, or component library.
- Reuse existing components and utilities wherever they fit.
- Follow the naming, file layout, and code style already present.
- Do not upgrade, replace, or remove existing dependencies to make this
  feature fit. Adapt the feature to the app, not the app to the feature.
- Do not break existing functionality. If a change is genuinely required in
  existing code, make the smallest one that works and say so.
- If something in these instructions conflicts with how the application is
  built, follow the application and explain the deviation.

## Final Verification

Before you report the work as done:

1. Re-read the acceptance criteria above and check each one against what you
   actually built.
2. Run the application and exercise the feature end to end.
3. Run the existing test suite and confirm you have broken nothing.
4. Check the feature on mobile, tablet, and desktop widths.
5. Check keyboard navigation and focus handling.
6. Summarize what changed: files added, files modified, and anything you
   deliberately did differently because of how this application is built.

If any acceptance criterion is unmet, fix it before reporting completion.