---
id: S02
parent: M004
milestone: M004
provides:
  - Dark theme CSS custom property system (77 tokens) for downstream slices to consume
  - Mobile-safe responsive layout baseline
requires:
  []
affects:
  - S03
  - S04
key_files:
  - frontend/src/App.css
  - frontend/index.html
key_decisions:
  - 77 semantic CSS custom properties in :root (vs ~30 planned) to fully eliminate all hardcoded colors
  - Cyan #22d3ee replaces indigo #6366f1 as the accent color throughout the UI
  - Dark-tinted badge backgrounds for readable status badges on dark theme
  - overflow-x:hidden on html,body as global mobile overflow safety net
  - mode-toggle label uses overflow:hidden + text-overflow:ellipsis for controlled truncation on mobile
patterns_established:
  - All colors in App.css use var(--*) references — any future CSS must use existing tokens or define new ones in the :root block, never hardcode hex/rgba values
  - Mobile overflow prevention: html,body overflow-x:hidden as global safety net, plus targeted flex-wrap/overflow:hidden on components that use white-space:nowrap
observability_surfaces:
  - none
drill_down_paths:
  - .gsd/milestones/M004/slices/S02/tasks/T01-SUMMARY.md
  - .gsd/milestones/M004/slices/S02/tasks/T02-SUMMARY.md
duration: ""
verification_result: passed
completed_at: 2026-03-30T06:42:29.412Z
blocker_discovered: false
---

# S02: Dark Theme + Cyan Accents + Mobile Responsive Fix

**Replaced all 193 hex colors and 24 rgba values in App.css with 77 CSS custom properties establishing a dark theme with cyan accents, fixed mobile horizontal overflow, and updated HTML metadata.**

## What Happened

This slice converted the entire Chrysopedia frontend from hardcoded colors to a semantic CSS custom property system and fixed mobile responsive issues.

**T01 — CSS Custom Properties + Dark Theme:** Audited all ~1770 lines of App.css, identified 193 hex color references and 24 rgba values, and replaced every one with `var(--*)` references. Defined 77 semantic tokens in a `:root` block covering: page/surface/input backgrounds, primary/secondary/muted text, borders, cyan accent (replacing indigo throughout), status badge variants (pending/approved/edited/rejected with dark-appropriate tints), button states, shadows, overlays, header/transcript backgrounds, error states, and active tab/filter indicators. The token count grew from the planned ~30 to 77 because full coverage of the existing design required finer semantic distinctions — e.g., separate hover, focus, and subtle variants for the accent color, distinct badge background/text pairs for dark readability, and separate shadow weights for cards vs dialogs.

**T02 — Mobile Responsive + HTML Metadata:** Added `overflow-x: hidden` to `html, body` as a global safety net against horizontal scroll. Fixed three specific overflow sources: mode-toggle label (added `overflow: hidden; text-overflow: ellipsis; max-width: 6rem`), creator-row stats (added `flex-wrap: wrap` in the 640px media query), and app-header__right (added `flex-wrap: wrap`). Updated index.html title from "Chrysopedia Admin" to "Chrysopedia" and added `<meta name="theme-color" content="#0a0a12">` for mobile browser chrome coloring. Deployed to ub01 and visually verified at desktop (1280×800) and mobile (390×844) viewports — dark theme renders correctly, no horizontal scrollbar on any tested page.

## Verification

All slice-level verification checks pass:
- `npm run build` exits 0 (clean build, no warnings)
- Hex colors outside `:root` block: 0 (all 77 hex values are inside `:root` definitions only)
- CSS `var(--` references: 217 (exceeds 190+ threshold)
- `rgba()` outside `:root` block: 0
- `overflow-x` rule present in App.css
- `<title>Chrysopedia</title>` confirmed in index.html
- `<meta name="theme-color">` confirmed in index.html
- Browser verification at 390px mobile viewport: scrollWidth === clientWidth (no horizontal overflow)
- Visual verification on Home, Topics, and Creators pages at both desktop and mobile viewports confirms dark theme renders correctly

## Requirements Advanced

None.

## Requirements Validated

None.

## New Requirements Surfaced

None.

## Requirements Invalidated or Re-scoped

None.

## Deviations

Token count grew from planned ~30 to 77 CSS custom properties — needed finer semantic granularity to fully eliminate all hardcoded colors. `.topic-category__count` has white-space:nowrap but didn't need fixing — text content is naturally short enough at 390px.

## Known Limitations

Creators page returns API 422 on ub01 — this is a pre-existing backend issue (addressed in S01), not caused by this slice. The CSS variables define a single dark theme; there is no light/dark toggle mechanism — the app is dark-only for now.

## Follow-ups

None.

## Files Created/Modified

- `frontend/src/App.css` — Added 77 CSS custom properties in :root block, replaced all 193 hex colors and 24 rgba values with var(--*) references, added html/body overflow-x:hidden, fixed mode-toggle label truncation, creator-row stats wrapping, and header flex-wrap for mobile
- `frontend/index.html` — Changed title from 'Chrysopedia Admin' to 'Chrysopedia', added <meta name="theme-color" content="#0a0a12">
