---
id: S05
parent: M006
milestone: M006
provides:
  - 7 topic categories with card grid layout
  - Music Theory category with 8 sub-topics in canonical_tags.yaml
  - Badge CSS for music-theory category
requires:
  []
affects:
  - S06
key_files:
  - config/canonical_tags.yaml
  - frontend/src/pages/TopicsBrowse.tsx
  - frontend/src/App.css
key_decisions:
  - D020: 3px colored left border + dot for category card visual differentiation — subtler than full colored header, maintains dark theme
  - Client-side technique count via sub_topics.reduce() — no API changes needed
  - Warm orange-gold (#3b2506/#fdba74) for Music Theory badge — visually distinct from existing 6 category colors
patterns_established:
  - Category card pattern: colored left-border + dot using badge CSS custom properties for visual differentiation in card grids
observability_surfaces:
  - none
drill_down_paths:
  - .gsd/milestones/M006/slices/S05/tasks/T01-SUMMARY.md
  - .gsd/milestones/M006/slices/S05/tasks/T02-SUMMARY.md
duration: ""
verification_result: passed
completed_at: 2026-03-30T11:53:32.315Z
blocker_discovered: false
---

# S05: Topics Page Redesign + Music Theory Category

**Redesigned Topics browse page from vertical accordion to responsive 2-column card grid layout with 7 categories (added Music Theory) featuring colored accents, descriptions, summary stats, and expand/collapse sub-topic lists.**

## What Happened

This slice delivered two changes: adding Music Theory as the 7th canonical topic category, and rewriting the Topics browse page layout from a flat accordion list to a responsive card grid.

**T01 — Music Theory category addition.** Added "Music Theory" with 8 sub-topics (harmony, chord progressions, scales, rhythm, time signatures, melody, counterpoint, song keys) to `config/canonical_tags.yaml` on ub01. The API immediately reflected the change — no container restart needed. Also added warm orange-gold badge CSS (`--color-badge-cat-music-theory-bg: #3b2506`, `--color-badge-cat-music-theory-text: #fdba74`) to App.css, visually distinct from the existing 6 category colors (teal, purple, blue, amber, green, pink).

**T02 — Card grid layout rewrite.** Replaced the `.topics-list` single-column accordion with a `.topics-grid` CSS grid layout: 2 columns on desktop (≥640px), 1 column on mobile. Each category card has: a 3px colored left border using the category's badge CSS custom property, a small colored dot next to the category name, description text, summary stats line (sub-topic count + total technique count computed client-side via `sub_topics.reduce()`), and an expand/collapse toggle revealing sub-topics as search links with per-sub-topic technique and creator counts. The filter input narrows visible cards by matching category name + sub-topic names. All existing functionality preserved — expand/collapse, filter, sub-topic → `/search?q={name}&scope=topics` navigation.

Frontend build passed cleanly. Deployed to ub01 via Docker Compose rebuild. Browser verification confirmed 2-column desktop grid, 1-column mobile responsive layout, filter narrowing, and all 7 categories with correct visual differentiation.

## Verification

1. API returns 7 categories including Music Theory — `curl -s http://ub01:8096/api/v1/topics | python3 assert 7 categories` → PASS
2. CSS contains music-theory badge rules — `grep -c music-theory frontend/src/App.css` → 3 matches
3. Frontend production build succeeds — `npm run build` → 778ms, 0 errors
4. Deployed JS bundle contains new card classes — `curl CSS/JS bundles | grep topic-card/topics-grid` → present
5. Browser: desktop 2-column grid layout visible at 1280×800 viewport
6. Browser: mobile 1-column layout visible at 390×844 viewport
7. Browser: filter "music" narrows to Music Theory card only
8. Browser: expand/collapse toggles work, sub-topics listed with counts
9. Browser: Music Theory card shows orange-gold accent color, all 8 sub-topics visible

## Requirements Advanced

- R008 — Enhanced from 6-category accordion to 7-category responsive card grid with descriptions, stats, and color-coded cards

## Requirements Validated

None.

## New Requirements Surfaced

None.

## Requirements Invalidated or Re-scoped

None.

## Deviations

T02 plan verification expected to grep HTML for `topic-category` classes, but the SPA serves an empty shell — class names live in the JS bundle. Adapted to check bundle contents instead. Docker web container rebuild initially returned cached layers despite --no-cache flag — required a second rebuild to pick up source changes.

## Known Limitations

Music Theory category has 0 techniques and 0 creators — content will populate as videos with music theory tags are processed through the pipeline. The 7th card sits alone on the last row of the 2-column grid (odd number), which is visually acceptable but could be improved with a different grid strategy if more categories are added.

## Follow-ups

None.

## Files Created/Modified

- `config/canonical_tags.yaml` — Added Music Theory as 7th category with 8 sub-topics (harmony, chord progressions, scales, rhythm, time signatures, melody, counterpoint, song keys)
- `frontend/src/pages/TopicsBrowse.tsx` — Rewritten from vertical accordion to responsive 2-column card grid with colored accents, descriptions, summary stats, and expand/collapse
- `frontend/src/App.css` — Added music-theory badge CSS custom properties and class; replaced .topics-list styles with .topics-grid/.topic-card card grid styles
