Rewrite ~120 validation error messages across 17 English lesson modules
and their localized variants (ar, de, es, pl, uk) to use concept questions,
property hints, and directional nudges instead of revealing the exact
CSS property-value answers.
Priority modules (flexbox, box-model, colors, positioning) fully rewritten.
All remaining CSS modules updated. Only message strings changed — no
validation logic modifications.
- Add CSS Colors, Typography, Advanced Selectors, and Grid modules
- Remove deprecated HTML Marquee module from all languages
- Remove redundant div & span lesson from HTML Block & Inline
- Move SVG module from HTML to CSS section
- Enhance first lessons with comprehensive explanations:
- Flexbox: historical context, axes concept
- Colors: named colors, background-color explained
- Grid: comparison to Flexbox, key properties
- Swap header logo highlight (CRISPIES instead of CODE)
- Use English fallbacks for new modules in non-EN languages
- Fix test to include 'playground' mode
New path: 19 modules (~78 lessons) vs previous 16 modules (62 lessons)
🤖 Generated with [Claude Code](https://claude.com/claude-code)
- Hello World lesson now styles plain text (no h1 required)
- Added syntax examples to CSS Variables, calc(), Media Queries, Flexbox, Grid
- Added goodbye/offboarding module with contribution encouragement
- Add <kbd> tags to CSS property values and selectors in task descriptions
- Add solution code to all lessons for better guidance
- Improve animation contrast in transitions lesson (black/white instead
of similar purples, dramatic color changes for visibility)
- Simplify validation messages with kbd formatting
