Add K-Nearest Neighbors interactive lesson in Vietnamese

[LMK89]

Summary

Added a comprehensive interactive educational lesson on K-Nearest Neighbors (KNN) algorithm in Vietnamese, including visual demonstrations, interactive demos, and self-grading quizzes.

Changes

• New lesson file: 2026-08-29-knn-k-nearest-neighbors-1600b4a3.html

  • Complete HTML5 lesson with embedded CSS and JavaScript
  • Dark/light theme toggle with localStorage persistence
  • Responsive design (mobile-friendly)

• Content sections:

  • Quick warmup quiz (3 questions) to activate prior knowledge
  • Formal definition of KNN algorithm with ASCII visualization
  • Real-world example: fruit classification (apples vs oranges) with sample dataset
  • Four detailed state comparisons (k=1, optimal k, k too large, missing data normalization)
  • Comprehensive comparison table
  • Interactive step-by-step demo calculating Euclidean distances and voting
  • Good vs bad data characteristics
  • Self-grading quiz with 3 conceptual questions

• Interactive features:

  • Warmup section with fill-in-the-blank and matching exercises
  • Live KNN demo: input new fruit properties, select k value, see distance calculations and voting results
  • Random data generator for demo exploration
  • Quiz with instant feedback and scoring

• Updated README.md: Added entry for the new KNN lesson to the course index

Implementation Details

• Uses CSS custom properties (CSS variables) for theming
• Smooth animations (fadeInDown, slideUp, slideDown, pulse) for visual feedback
• Euclidean distance calculation: √((x₁-x₂)² + (y₁-y₂)²)
• Vote-based classification with tie-breaking
• Responsive grid layout (single column on mobile, two columns on desktop)
• No external dependencies — pure HTML/CSS/JavaScript

https://claude.ai/code/session_01T2h1h1r7crG2ubboi4uKR5