- Implement 50/50 split layout (left: instructions + editor, right: preview)
- Replace always-visible sidebar with slide-out drawer menu
- Move footer, progress, and settings into sidebar
- Add toggleable expected result overlay (hidden by default)
- Create new hint system with step progress indicators
- Add ghost button styles for modal and text button for sidebar reset
- Fix HTML lesson task instruction and typo ("important" not "importing")
- Add padding to preview frames to prevent corner clipping
- Optimize layout for iPadOS and tablet devices
- 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
