:root {
  --primary-color: #667eea;
  --secondary-color: #764ba2;
  --text-color: #333;
  --bg-color: #f8f9fa;
  --card-bg: #ffffff;
  --border-color: #e0e0e0;
}

body.ui-style-3 {
  font-size: 16px;
}

.container {
  animation: fadeIn 0.5s ease-in;
}

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

.video-card, .related-card {
  cursor: pointer;
}

.back-to-top {
  position: fixed;
  bottom: 30px;
  right: 30px;
  background: var(--primary-color);
  color: white;
  width: 50px;
  height: 50px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  box-shadow: 0 4px 12px rgba(0,0,0,0.2);
  opacity: 0;
  visibility: hidden;
  transition: all 0.3s;
  z-index: 999;
}

.back-to-top.show {
  opacity: 1;
  visibility: visible;
}

.back-to-top:hover {
  background: var(--secondary-color);
  transform: translateY(-3px);
}