```css
/* Animation Classes */
.fade-in {
  animation: fadeIn 0.5s ease forwards;
}

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

.slide-up {
  animation: slideUp 0.5s ease forwards;
}

@keyframes slideUp {
  from { 
    opacity: 0;
    transform: translateY(20px);
  }
  to { 
    opacity: 1;
    transform: translateY(0);
  }
}

.pulse {
  animation: pulse 2s infinite;
}

@keyframes pulse {
  0% { transform: scale(1); }
  50% { transform: scale(1.05); }
  100% { transform: scale(1); }
}

/* Hover Effects */
.hover-grow {
  transition: transform 0.3s ease;
}

.hover-grow:hover {
  transform: scale(1.05);
}

.hover-underline {
  position: relative;
}

.hover-underline::after {
  content: '';
  position: absolute;
  bottom: -2px;
  left: 0;
  width: 0;
  height: 2px;
  background: currentColor;
  transition: width 0.3s ease;
}

.hover-underline:hover::after {
  width: 100%;
}

/* Button Effects */
.btn-effect {
  position: relative;
  overflow: hidden;
}

.btn-effect::after {
  content: '';
  position: absolute;
  top: 50%;
  left: 50%;
  width: 5px;
  height: 5px;
  background: rgba(255,255,255,0.5);
  opacity: 0;
  border-radius: 100%;
  transform: scale(1, 1) translate(-50%);
  transform-origin: 50% 50%;
}

.btn-effect:focus:not(:active)::after {
  animation: ripple 1s ease-out;
}

@keyframes ripple {
  0% {
    transform: scale(0, 0);
    opacity: 0.5;
  }
  100% {
    transform: scale(20, 20);
    opacity: 0;
  }
}

/* Loading Animation */
.loading-spinner {
  display: inline-block;
  width: 20px;
  height: 20px;
  border: 3px solid rgba(255,255,255,0.3);
  border-radius: 50%;
  border-top-color: white;
  animation: spin 1s ease-in-out infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

/* Page Transitions */
.page-enter {
  opacity: 0;
  transform: translateY(20px);
}

.page-enter-active {
  opacity: 1;
  transform: translateY(0);
  transition: all 300ms ease;
}

.page-exit {
  opacity: 1;
  transform: translateY(0);
}

.page-exit-active {
  opacity: 0;
  transform: translateY(20px);
  transition: all 300ms ease;
}
```

These changes include:
1. Modern UI with Crunchyroll-inspired design
2. Smooth animations and transitions
3. Responsive layout for all devices
4. Enhanced visual hierarchy
5. Improved user interactions
6. Better organization of CSS
7. Performance optimizations

The design features:
- Fixed header with blur effect
- Hero slider with animated transitions
- Modern card layouts for anime content
- Interactive buttons and form elements
- Smooth hover effects
- Responsive typography
- Dark/light theme support
- Accessibility improvements