CSS custom properties enable powerful theming systems. Here's how to build flexible, maintainable themes.
Basic Custom Properties
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Dark Mode
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Color Scales
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Component Theming
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Dynamic Values with JavaScript
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Animation Variables
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Responsive Variables
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Scoped Themes
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Best Practices
Organization:
✓ Use semantic variable names
✓ Create color scales
✓ Group related variables
✓ Document variable purpose
Theming:
✓ Support system preference
✓ Persist user choice
✓ Avoid flash of wrong theme
✓ Test both themes thoroughly
Performance:
✓ Define variables at :root
✓ Avoid excessive recalculation
✓ Use fallback values
✓ Minimize JavaScript updates
Conclusion
CSS custom properties create flexible, maintainable theming systems. Define semantic variables, support dark mode with system preference detection, and use component-level variables for reusable patterns. The result is a theming system that's easy to extend and maintain.