style(playground): redesign UI with modern minimal grid aesthetic

[AVGVSTVS96]

Add a clean, dark theme inspired by modern developer tool sites:

• Subtle grid background pattern with layered line densities
• Deep dark color palette with indigo accent color
• Gradient text effects on headings
• Improved prose styling for code blocks and content
• Cleaned up footer layout with GitHub link
• Removed unused App.css legacy styles

[changeset-bot]

⚠️ No Changeset found

Latest commit: ab4c2ae

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Project	Deployment	Preview	Comments	Updated (UTC)
react-shiki	Ready	Preview	Comment	Dec 5, 2025 11:13pm

[claude]

Claude finished @AVGVSTVS96's task —— View job

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Code Review for PR #114

Reviewing the playground UI redesign changes...

Tasks:

• Read and analyze modified files (App.tsx, index.css)
• Review deleted App.css file impact
• Check code quality and best practices
• Assess performance and security considerations
• Determine if changeset is needed
• Provide comprehensive feedback

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✅ Review Summary

This PR successfully implements a clean, modern dark theme for the playground with good attention to detail and best practices.

🎯 Changeset Assessment

No changeset needed - This only affects the playground demo app, not the published react-shiki package. The playground is marked as private: true and is not part of the package distribution.

📋 Code Quality & Architecture

Excellent Practices:

• Clean separation of concerns: Properly removed unused CSS (App.css) and consolidated styles in index.css
• CSS Custom Properties: Well-organized design token system with semantic naming (--bg, --text, --accent, etc.)
• Performance optimizations:
  • Font rendering optimizations (text-rendering: optimizeLegibility, -webkit-font-smoothing)
  • Minimal CSS with good specificity management
• Accessibility: Proper color contrast with dark theme and color-scheme: dark
• Modern CSS: Uses CSS cascade layers and proper Tailwind CSS v4 integration

Styling Implementation:

/* Well-structured design tokens */
:root {
  --bg: #0a0a0a;
  --bg-secondary: #111111;
  --border: rgba(255, 255, 255, 0.1);
  --text: rgba(255, 255, 255, 0.9);
  --accent: #a78bfa;
}

The color palette is cohesive and provides good contrast ratios for readability.

🔧 Component Updates (App.tsx)

• Clean grid layout implementation
• Proper TypeScript usage
• Good component structure with semantic HTML

⚡ Performance Considerations

• Positive: Removed unused styles, optimized font loading
• Positive: Efficient CSS with minimal specificity conflicts
• Positive: Good use of CSS custom properties for theme consistency

🔒 Security

No security concerns identified. All changes are styling-related with no dynamic content or external dependencies.

🚀 Recommendations

1. Minor Enhancement: Consider adding a CSS transition for the accent color hover states to match the existing link transitions:

   a {
     transition: opacity 0.15s;
   }

2. Documentation: The grid background effect mentioned in the PR description isn't visible in the current CSS - consider adding a comment if this is intentional or will be added later.

✨ Overall Assessment

This is a high-quality implementation that:

• ✅ Follows modern CSS best practices
• ✅ Maintains good performance characteristics
• ✅ Provides excellent code organization
• ✅ Successfully achieves the design goals

Recommendation: Approved - This PR is ready to merge with no blocking issues.

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