Bits of .NET

🎨 One Variable Change, Whole Site Updates

Sass variables compile once. CSS variables update at runtime. Dark mode, dynamic theming, component libraries — finally possible.

📦 Defining and Using Variables

/* Define on :root (global) */
:root {
  --primary-color: #3498db;
  --secondary-color: #2ecc71;
  --spacing-unit: 8px;
  --border-radius: 4px;
  --font-size-base: 16px;
}

/* Use variables */
.button {
  background-color: var(--primary-color);
  padding: var(--spacing-unit) calc(var(--spacing-unit) * 2);
  border-radius: var(--border-radius);
  font-size: var(--font-size-base);
}

.button-secondary {
  background-color: var(--secondary-color);
}

🎯 Dynamic Dark Mode

:root {
  --bg-color: #ffffff;
  --text-color: #333333;
  --card-bg: #f5f5f5;
}

[data-theme='dark'] {
  --bg-color: #1a1a2e;
  --text-color: #e0e0e0;
  --card-bg: #16213e;
}

body {
  background-color: var(--bg-color);
  color: var(--text-color);
  transition: background-color 0.3s, color 0.3s;
}

.card {
  background-color: var(--card-bg);
}

✅ JavaScript Integration

// Get variable value
const primaryColor = getComputedStyle(document.documentElement)
    .getPropertyValue('--primary-color');

// Set variable value
document.documentElement.style.setProperty('--primary-color', '#e74c3c');

// Dark mode toggle
function toggleDarkMode() {
  const isDark = document.body.dataset.theme === 'dark';
  document.body.dataset.theme = isDark ? 'light' : 'dark';
}

// Responsive variables
const setResponsiveVars = () => {
  const width = window.innerWidth;
  if (width < 768) {
    document.documentElement.style.setProperty('--spacing-unit', '4px');
  } else {
    document.documentElement.style.setProperty('--spacing-unit', '8px');
  }
};
window.addEventListener('resize', setResponsiveVars);

💡 Browser Support

• Chrome 49+ ✅
• Firefox 31+ ✅
• Safari 9.1+ ✅
• Edge 15+ ✅
• IE: ❌ (use fallback: color: #333; color: var(--text-color);)