:root {
  --font-sans: 'Inter', sans-serif;
  --font-display: 'Montserrat', sans-serif;

  --color-primary: var(--bs-primary);
  --color-secondary: var(--bs-secondary);
  --color-danger: var(--bs-danger);

  --shadow-sm: 0 1px 2px rgba(0,0,0,.05);
  --shadow-md: 0 4px 12px rgba(0,0,0,.08);
  --shadow-lg: 0 10px 30px rgba(0,0,0,.15);

  --border-radius-card: 1.5rem;
  --border-radius-btn: .75rem;

  --transition-fast: .2s cubic-bezier(0.25, 0.46, 0.45, 0.94);
  --transition-slow: .4s cubic-bezier(0.25, 0.46, 0.45, 0.94);
}

body {
  font-family: var(--font-sans);
}

html[data-bs-theme='light'] body {
  background: radial-gradient(1200px circle at 10% 10%, #e6f0ff 0, transparent 40%), radial-gradient(1200px circle at 90% 30%, #ffe9f0 0, transparent 40%), linear-gradient(180deg, #f8fafc 0, #eef2f7 100%);
  color: var(--bs-body-color);
}

html[data-bs-theme='dark'] body {
  background: radial-gradient(1000px circle at 10% 10%, rgba(60,130,246,.15) 0, transparent 40%), radial-gradient(1000px circle at 90% 30%, rgba(249,112,154,.12) 0, transparent 40%), linear-gradient(180deg, #0b1220 0, #0d1324 100%);
  color: var(--bs-body-color);
}

.navbar-brand {
  font-family: var(--font-display);
  font-weight: 700;
  letter-spacing: -0.05em;
  font-size: 1.5rem;
  transition: transform var(--transition-fast);
}

.navbar-brand:hover {
  transform: scale(1.02);
}

.hero {
  border-radius: var(--border-radius-card);
  background: linear-gradient(135deg, rgba(0,123,255,.15), rgba(111,66,193,.15));
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  padding: 3rem;
  animation: fadeIn 1s var(--transition-slow);
  box-shadow: var(--shadow-md);
}

.card {
  border-radius: var(--border-radius-card);
  transition: transform var(--transition-fast), box-shadow var(--transition-fast), border-color var(--transition-fast);
  border: 1px solid var(--bs-border-color-translucent);
}

.card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-lg);
}

.table thead th {
  letter-spacing: .02em;
  font-weight: 500;
}

.table tbody tr {
  transition: transform .12s ease, background-color .12s ease;
  cursor: pointer;
}

.table tbody tr:hover:not(.collapse-row) {
  transform: translateY(-1px);
}

.schedule-table td, .schedule-table th {
  white-space: nowrap;
}

.btn {
  border-radius: var(--border-radius-btn);
  font-weight: 500;
  transition: transform var(--transition-fast), box-shadow var(--transition-fast);
}

.btn:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.form-control:focus {
  box-shadow: 0 0 0 .2rem rgba(13,110,253,.15);
}

.theme-toggle {
  border-radius: 50%;
  width: 40px;
  height: 40px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: transform var(--transition-fast), background-color var(--transition-fast), color var(--transition-fast);
}

.theme-toggle:hover {
  transform: scale(1.1);
  background-color: var(--bs-secondary-bg);
  color: var(--color-primary);
}

.empty {
  border-radius: 2rem;
  background: linear-gradient(135deg, rgba(0,0,0,.03), rgba(0,0,0,.02));
  padding: 2.5rem;
  text-align: center;
  border: 1px dashed var(--bs-border-color-translucent);
}

.empty .bi {
  font-size: 3rem;
  color: var(--color-secondary);
  animation: bounceIn 1s var(--transition-slow);
}

.teacher-photo {
  width: 100%;
  height: 200px;
  object-fit: cover;
  border-top-left-radius: var(--border-radius-card);
  border-top-right-radius: var(--border-radius-card);
}

.teacher-card .card-body {
  padding-top: 1rem;
}

.collapse-row td {
    border-top: none !important;
    padding-top: 0;
    padding-bottom: 0;
}

.collapse-row .p-3 {
    margin: 0.5rem 0;
}

.schedule-card .card-body {
  padding: 1.5rem;
}

.schedule-card .card-footer {
  padding: 1rem 1.5rem;
  background-color: transparent;
  border-top: 1px solid var(--bs-border-color-translucent);
}

.comment-container {
  background-color: var(--bs-light-bg-subtle);
  transition: background-color var(--transition-fast);
}

html[data-bs-theme='dark'] .comment-container {
  background-color: var(--bs-tertiary-bg);
}

@media (max-width: 991.98px) {
  .navbar-brand {
    font-size: 1.25rem;
  }
  .navbar-collapse {
    text-align: center;
  }
  .d-lg-block {
    display: none !important;
  }
}

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

@keyframes bounceIn {
  0% { transform: scale(0.5); opacity: 0; }
  60% { transform: scale(1.1); opacity: 1; }
  100% { transform: scale(1); }
}