:root {
  --edu-gradient: linear-gradient(135deg, #4f46e5 0%, #22d3ee 100%);
  --theme-toggle-sun-core: #facc15;
  --theme-toggle-sun-rays: rgba(251, 191, 36, 0.85);
  --theme-toggle-moon-body: #f8fafc;
  --theme-toggle-moon-cutout: #f5f7fb;
  --theme-toggle-moon-shadow: rgba(148, 163, 184, 0.45);
}

:root[data-bs-theme='dark'] {
  --edu-gradient: linear-gradient(135deg, #312e81 0%, #0f172a 100%);
  --theme-toggle-moon-body: #e2e8f0;
  --theme-toggle-moon-cutout: #020617;
  --theme-toggle-moon-shadow: rgba(15, 23, 42, 0.65);
}

:root[data-bs-theme='dark'] body {
  background-color: #020617;
  color: #e2e8f0;
}

:root[data-bs-theme='dark'] .text-secondary {
  color: #94a3b8 !important;
}

:root[data-bs-theme='dark'] .bg-white,
:root[data-bs-theme='dark'] .bg-light,
:root[data-bs-theme='dark'] .card,
:root[data-bs-theme='dark'] .list-group-item,
:root[data-bs-theme='dark'] .feature-card,
:root[data-bs-theme='dark'] .review-card,
:root[data-bs-theme='dark'] article {
  background-color: #0f172a !important;
  color: inherit;
  border-color: rgba(148, 163, 184, 0.25) !important;
}

:root[data-bs-theme='dark'] .list-group-item {
  border-color: rgba(148, 163, 184, 0.25);
}

:root[data-bs-theme='dark'] .hero-card {
  background: var(--edu-gradient);
  box-shadow: 0 16px 45px rgba(15, 23, 42, 0.45);
}

:root[data-bs-theme='dark'] .hero-card .btn-outline-light {
  border-color: rgba(255, 255, 255, 0.6);
}

:root[data-bs-theme='dark'] .hero-card .btn-outline-light:hover {
  background-color: rgba(255, 255, 255, 0.15);
}

.theme-toggle-btn {
  gap: 0.5rem;
  border-radius: 999px;
  padding-inline: 0.85rem;
  transition: background-color 0.2s ease, box-shadow 0.2s ease;
}

.theme-toggle-icon {
  width: 1.85rem;
  height: 1.85rem;
  position: relative;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.theme-toggle-sun,
.theme-toggle-moon {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: opacity 0.25s ease, transform 0.25s ease;
}

.theme-toggle-sun .sun-core {
  width: 1rem;
  height: 1rem;
  border-radius: 50%;
  background: radial-gradient(circle at 35% 35%, #fff8e1, var(--theme-toggle-sun-core));
  box-shadow: 0 0 12px var(--theme-toggle-sun-rays);
}

.theme-toggle-sun .sun-rays {
  position: absolute;
  width: 1.5rem;
  height: 1.5rem;
  border-radius: 50%;
  border: 2px solid var(--theme-toggle-sun-rays);
  opacity: 0.9;
}

.theme-toggle-moon .moon-body {
  width: 1rem;
  height: 1rem;
  border-radius: 50%;
  background: var(--theme-toggle-moon-body);
  box-shadow: 0 0 10px var(--theme-toggle-moon-shadow);
  position: relative;
}

.theme-toggle-moon .moon-body::after {
  content: "";
  position: absolute;
  width: 1rem;
  height: 1rem;
  border-radius: 50%;
  background: var(--theme-toggle-moon-cutout);
  left: 35%;
  top: -4%;
  box-shadow: inset 0 0 6px rgba(15, 23, 42, 0.3);
}

.theme-toggle-moon .moon-body::before {
  content: "";
  position: absolute;
  width: 0.25rem;
  height: 0.25rem;
  border-radius: 50%;
  background: rgba(148, 163, 184, 0.45);
  top: 18%;
  left: 25%;
  box-shadow:
    0.4rem 0.1rem 0 0 rgba(148, 163, 184, 0.3),
    0.15rem 0.35rem 0 0 rgba(148, 163, 184, 0.35);
}

:root[data-bs-theme='dark'] .deck-card:hover {
  box-shadow: 0 16px 32px rgba(15, 23, 42, 0.65);
}

:root[data-bs-theme='dark'] .flashcard-item:hover {
  border-left-color: #6366f1;
  background-color: rgba(99, 102, 241, 0.15);
}

body {
  background-color: #f5f7fb;
  font-family: "Inter", "Segoe UI", system-ui, -apple-system, "Helvetica Neue", Arial, sans-serif;
}

main {
  padding-block: 2.5rem;
}

.hero-card {
  background: var(--edu-gradient);
  color: #fff;
  border: none;
  box-shadow: 0 16px 45px rgba(79, 70, 229, 0.22);
}

.hero-card .btn-outline-light {
  color: #fff;
  border-color: rgba(255, 255, 255, 0.75);
}

.hero-card .btn-outline-light:hover {
  background-color: rgba(255, 255, 255, 0.12);
}

.deck-card {
  transition: transform 0.18s ease, box-shadow 0.18s ease;
}

.deck-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 16px 32px rgba(15, 23, 42, 0.1);
}

.flashcard-item {
  border-left: 4px solid transparent;
  transition: border-color 0.2s ease, background-color 0.2s ease;
}

.flashcard-item:hover {
  border-left-color: #4f46e5;
  background-color: rgba(79, 70, 229, 0.05);
}

.badge-difficulty {
  text-transform: uppercase;
  font-size: 0.7rem;
  letter-spacing: 0.08em;
}

.badge-difficulty.easy {
  background-color: rgba(74, 222, 128, 0.15);
  color: #15803d;
}

.badge-difficulty.medium {
  background-color: rgba(251, 191, 36, 0.2);
  color: #b45309;
}

.badge-difficulty.hard {
  background-color: rgba(239, 68, 68, 0.18);
  color: #b91c1c;
}

.review-card {
  background: #ffffff;
  border-radius: 24px;
  box-shadow: 0 16px 45px rgba(79, 70, 229, 0.15);
}

.review-card .card-question {
  font-size: 1.2rem;
  line-height: 1.6rem;
}

.progress-bar-rounded {
  height: 0.6rem;
  border-radius: 999px;
}

.import-textarea {
  min-height: 220px;
}

.chart-bar {
  border-radius: 12px;
  transition: transform 0.2s ease;
}

.chart-bar:hover {
  transform: translateY(-4px);
}

.pill {
  border-radius: 999px;
}

.toast-container .toast {
  width: 100%;
}

@media (max-width: 767px) {
  main {
    padding-block: 1.75rem;
  }
}