---
id: S03
parent: M010
milestone: M010
provides:
  - Category accent colors on SubTopicPage (border + badge) and SearchResults (badge)
  - Page-enter fade-in animation on all 7 public pages
  - Shared catSlug utility at frontend/src/utils/catSlug.ts
requires:
  - slice: S01
    provides: SubTopicPage component and .subtopic-page CSS class
affects:
  []
key_files:
  - frontend/src/utils/catSlug.ts
  - frontend/src/pages/SubTopicPage.tsx
  - frontend/src/pages/SearchResults.tsx
  - frontend/src/pages/TopicsBrowse.tsx
  - frontend/src/App.css
key_decisions:
  - Extracted catSlug into shared utils/ directory — establishes pattern for cross-page helper reuse
  - Applied page-enter animation via CSS selector list rather than adding className to each TSX file — zero component churn
  - Placed category badge in subtitle row for clean visual hierarchy on SubTopicPage
patterns_established:
  - Shared utility pattern: frontend/src/utils/ for cross-page helpers
  - CSS-only page transitions via selector list targeting existing wrapper classes — no component changes needed
observability_surfaces:
  - none
drill_down_paths:
  - .gsd/milestones/M010/slices/S03/tasks/T01-SUMMARY.md
  - .gsd/milestones/M010/slices/S03/tasks/T02-SUMMARY.md
duration: ""
verification_result: passed
completed_at: 2026-03-31T06:28:12.150Z
blocker_discovered: false
---

# S03: Topic Color Coding & Visual Polish

**Added per-category accent colors (border + badge) to SubTopicPage and SearchResults, extracted catSlug to shared utility, and applied CSS-only page-enter fade-in animation to all 7 public pages.**

## What Happened

This slice delivered two complementary visual polish features:

**T01 — Category accent colors.** Extracted the `catSlug` helper from TopicsBrowse.tsx into `frontend/src/utils/catSlug.ts` for cross-page reuse. Applied category accent colors in two places: (1) SubTopicPage gets a 4px colored left border using `var(--color-badge-cat-{slug}-text)` and a colored category badge in the subtitle row; (2) SearchResults cards now render `topic_category` as a colored `badge--cat-{slug}` badge instead of plain text. All 7 category slugs (sound-design, mixing, synthesis, arrangement, workflow, mastering, music-theory) work against the CSS custom properties established in M004/S02.

**T02 — Page enter transitions.** Added a `@keyframes pageEnter` animation (opacity 0→1, translateY 8px→0, 250ms ease-out) applied via a CSS selector list targeting all 7 public page wrapper classes (.home, .topics-browse, .subtopic-page, .search-results-page, .creators-browse, .creator-detail, .technique-page). No TSX files were modified — the animation triggers on mount via existing class names.

Both tasks pass TypeScript type-checking and Vite production build with zero errors.

## Verification

TypeScript compilation (`npx tsc --noEmit`) and Vite production build (`npm run build`) both pass with zero errors. 49 modules transformed, production bundle produced at dist/. Verified catSlug utility is imported correctly by TopicsBrowse, SubTopicPage, and SearchResults. Verified pageEnter animation targets all 7 page wrapper classes.

## Requirements Advanced

None.

## Requirements Validated

None.

## New Requirements Surfaced

None.

## Requirements Invalidated or Re-scoped

None.

## Deviations

None. T02 used the CSS selector list approach (plan option #4) to avoid touching 7 TSX files — this was explicitly offered as an alternative in the plan.

## Known Limitations

None.

## Follow-ups

None.

## Files Created/Modified

- `frontend/src/utils/catSlug.ts` — New shared utility exporting catSlug(name) → CSS slug
- `frontend/src/pages/TopicsBrowse.tsx` — Import catSlug from shared utility instead of local definition
- `frontend/src/pages/SubTopicPage.tsx` — Added colored left border and category badge using catSlug
- `frontend/src/pages/SearchResults.tsx` — Replaced plain topic_category text with colored badge
- `frontend/src/App.css` — Added @keyframes pageEnter animation and applied to all 7 page wrapper classes; added subtopic-page border styles
