# Theme Surface Map

## Objective

Decide how page, card, popover, and dialog surfaces relate before each screen improvises.

A defined relationship between every layered surface in the app — page, card, input, popover, dialog, elevated — in each theme.

## 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. List every surface the app renders and place each at a defined level: the page background, cards and panels sitting on it, inputs sitting inside those, popovers and menus above them, and dialogs above everything.
2. Give adjacent levels enough separation to be seen as separate without a border. Two surfaces one step apart on the ramp look identical on a poorly calibrated laptop screen, which is what most people are using.
3. Verify the text and border tokens against every surface, not only against the page background. A muted text colour that reads comfortably on the page will often disappear on an elevated card in dark mode.
4. Restrict translucent surfaces to cases where what sits behind them is known and controlled. A frosted popover over a photograph, a video, or a syntax-highlighted code block has no predictable contrast, so give those an opaque variant.
5. In dark themes, express elevation primarily as a lighter surface rather than as a heavier shadow. A shadow on a near-black background is invisible, and the usual response — deepening it further — produces a dark halo instead of a sense of height.

## 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

- Adjacent surface levels must remain distinguishable on uncalibrated displays and at low brightness, or the card boundary that carries the whole layout simply disappears.
- Text and border contrast has to hold on every layer, since a token verified only against the page background will fail on the elevated surfaces where it is used most.
- Translucent surfaces over unknown content must be avoided or given an opaque fallback, because contrast over an arbitrary photograph or video frame cannot be guaranteed by any token.
- Shadows and overlays need a coherent dark-mode treatment. Elevation in dark themes comes from surface lightness, not from a shadow nobody can see against a near-black page.
- Nesting depth must be bounded. A card inside a panel inside a dialog runs out of distinct surface steps, so define what happens at the fourth level rather than letting it degrade into flat sameness.
- The backdrop behind a dialog belongs to the surface map too — an opacity chosen for a light theme dims a dark theme into an unreadable grey.
- Surface roles are named through Semantic Color Tokens; this brief defines their relationship and ordering, not a second naming scheme.

## 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

- [ ] Every surface in the app is assigned to a defined level in the map.
- [ ] Adjacent levels are visually distinguishable without relying on a border.
- [ ] Text and border tokens meet contrast requirements on every surface level, in every theme.
- [ ] Translucent surfaces are used only over controlled content, and an opaque variant exists.
- [ ] Dark themes convey elevation through surface lightness rather than shadow alone.
- [ ] Behaviour beyond the deepest defined nesting level is specified.
- [ ] Dialog backdrops are defined per theme rather than shared.
- [ ] 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.