- Interactive skill tree with dagre auto-layout and React Flow (15 math+logic nodes)
- Workbench with math input (LTR/RTL toggle), multiple choice, keyboard shortcuts
- Challenge verification engine with retry-based flow (no answer reveal until 3 failures)
- Scratchpad canvas with freehand drawing, text boxes, eraser, colors, and stroke sizes
- "Aprende primero" collapsible explanations on introductory challenges
- XP/level system, daily streaks, 7 achievements, progress persistence via Zustand
- Profile page with stats and achievement gallery
- Sidebar navigation with XP bar and streak badge
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
