Document learnings for creating effective lessons:
- Clear task instructions with selector and property
- Use codePrefix for context
- Simple, human-friendly values
- Named CSS colors for engagement
- Focused validations
- Semantic HTML in examples
- Remove presentational classes (.form-group, .required, .hint, .checkbox-group)
- Replace <span class="required">*</span> with plain * in label text
- Replace <div class="hint"> with semantic <small> element
- Simplify checkbox markup to use native label wrapping pattern
- Update previewBaseCSS to style semantic elements directly
- Add code quality standards to CLAUDE.md emphasizing WCAG compliance and native HTML
- Replace textarea with CodeMirror 6 for syntax highlighting
- Add Emmet abbreviation expansion (Tab to expand)
- Support HTML and CSS language modes with autocomplete
- Add dark theme matching app design
- Tab indentation with Shift-Tab for outdent
- Update help modal with Emmet shortcuts
- Add HTML mode support with new validation types (element_exists,
element_count, attribute_value, element_text, parent_child, sibling)
- Create 3 HTML lesson modules: Elements, Forms Basic, Forms Validation
- Implement side-by-side preview comparison (Your Output vs Expected)
- Add merge animation with "Perfect Match!" overlay on validation success
- Render expected output from solutionCode field in lesson JSON
- Update schema to support HTML mode and solutionCode
- Reorder modules: HTML first, then CSS, then Tailwind
- Update tests for new functionality
