.learning-shell {
  max-width: 1080px;
  margin: 0 auto;
  padding: 1.5rem 1rem 4rem;
}

.learning-breadcrumbs {
  display: flex;
  flex-wrap: wrap;
  gap: 0.45rem;
  margin-bottom: 1rem;
  color: var(--text-tertiary);
  font-size: 0.86rem;
}

.learning-breadcrumbs a,
.learning-link {
  color: var(--primary-500);
  text-decoration: none;
}

.learning-breadcrumbs a:hover,
.learning-link:hover {
  text-decoration: underline;
}

.learning-hero {
  position: relative;
  overflow: hidden;
  padding: clamp(1.5rem, 4vw, 3.25rem);
  border: 1px solid rgba(15, 185, 163, 0.28);
  border-radius: var(--radius-xl);
  background:
    radial-gradient(circle at 90% 10%, rgba(99, 102, 241, 0.2), transparent 34%),
    linear-gradient(135deg, rgba(15, 185, 163, 0.16), rgba(99, 102, 241, 0.08));
  box-shadow: var(--shadow-lg);
}

.learning-eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  margin-bottom: 0.85rem;
  padding: 0.35rem 0.68rem;
  border: 1px solid rgba(15, 185, 163, 0.35);
  border-radius: 999px;
  background: rgba(15, 185, 163, 0.1);
  color: var(--primary-600);
  font-size: 0.78rem;
  font-weight: 800;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.learning-hero h1 {
  max-width: 760px;
  margin: 0 0 0.85rem;
  font-size: clamp(2rem, 5vw, 3.6rem);
  line-height: 1.05;
}

.learning-hero-copy {
  max-width: 720px;
  margin: 0;
  color: var(--text-secondary);
  font-size: clamp(1rem, 2vw, 1.15rem);
  line-height: 1.7;
}

.learning-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-top: 1.35rem;
}

.learning-button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 0.72rem 1rem;
  border: 1px solid var(--primary-500);
  border-radius: 999px;
  background: var(--primary-500);
  color: #fff;
  font: inherit;
  font-size: 0.9rem;
  font-weight: 750;
  text-decoration: none;
  cursor: pointer;
  transition: transform var(--transition), background var(--transition), border-color var(--transition);
}

.learning-button:hover {
  border-color: var(--primary-400);
  background: var(--primary-400);
  transform: translateY(-1px);
}

.learning-button.secondary {
  border-color: var(--border-color);
  background: var(--bg-secondary);
  color: var(--text-primary);
}

.learning-button.secondary:hover {
  border-color: var(--primary-500);
  color: var(--primary-600);
}

.learning-button.ghost {
  border-color: transparent;
  background: transparent;
  color: var(--primary-600);
}

.learning-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 1rem;
  margin-top: 1.25rem;
}

.learning-card {
  display: flex;
  flex-direction: column;
  min-height: 100%;
  padding: 1.35rem;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  background: var(--bg-secondary);
  box-shadow: var(--shadow-sm);
}

.learning-card h2,
.learning-card h3 {
  margin: 0 0 0.55rem;
}

.learning-card p {
  margin: 0;
  color: var(--text-secondary);
  line-height: 1.65;
}

.learning-card .learning-actions {
  margin-top: auto;
  padding-top: 1rem;
}

.learning-card-icon {
  display: grid;
  width: 42px;
  height: 42px;
  margin-bottom: 0.85rem;
  place-items: center;
  border-radius: 13px;
  background: rgba(15, 185, 163, 0.12);
  font-size: 1.25rem;
}

.learning-section {
  margin-top: 2rem;
}

.learning-section > h2 {
  margin-bottom: 0.35rem;
  font-size: clamp(1.45rem, 3vw, 2rem);
}

.learning-section-intro {
  max-width: 760px;
  margin: 0 0 1rem;
  color: var(--text-secondary);
  line-height: 1.65;
}

.learning-progress {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.75rem;
  margin-top: 1.25rem;
}

.learning-stat {
  padding: 1rem;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  background: var(--bg-secondary);
}

.learning-stat strong {
  display: block;
  font-size: 1.4rem;
}

.learning-stat span {
  color: var(--text-secondary);
  font-size: 0.8rem;
}

.learning-note {
  margin-top: 1rem;
  padding: 1rem 1.1rem;
  border-left: 4px solid var(--primary-500);
  border-radius: var(--radius-md);
  background: rgba(15, 185, 163, 0.08);
  color: var(--text-secondary);
  line-height: 1.65;
}

.lesson-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 250px;
  gap: 1.25rem;
  align-items: start;
}

.lesson-article {
  padding: clamp(1.35rem, 4vw, 2.25rem);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-xl);
  background: var(--bg-secondary);
  box-shadow: var(--shadow-sm);
}

.lesson-article h1 {
  margin-bottom: 0.65rem;
  font-size: clamp(1.8rem, 4vw, 2.6rem);
}

.lesson-article h2 {
  margin: 2rem 0 0.65rem;
  scroll-margin-top: 90px;
}

.lesson-article p,
.lesson-article li {
  color: var(--text-secondary);
  line-height: 1.75;
}

.lesson-article li + li {
  margin-top: 0.45rem;
}

.lesson-meta {
  margin-bottom: 1.25rem;
  color: var(--text-tertiary);
  font-size: 0.84rem;
}

.lesson-nav {
  position: sticky;
  top: calc(var(--header-height) + 1rem);
  padding: 1rem;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  background: var(--bg-secondary);
}

.lesson-nav strong {
  display: block;
  margin-bottom: 0.65rem;
}

.lesson-nav a {
  display: block;
  padding: 0.38rem 0;
  color: var(--text-secondary);
  font-size: 0.84rem;
  text-decoration: none;
}

.lesson-nav a:hover {
  color: var(--primary-500);
}

.quiz-shell {
  max-width: 780px;
  margin: 0 auto;
}

.quiz-card {
  padding: clamp(1.25rem, 4vw, 2rem);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-xl);
  background: var(--bg-secondary);
  box-shadow: var(--shadow-lg);
}

.quiz-topline {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  margin-bottom: 0.75rem;
  color: var(--text-secondary);
  font-size: 0.85rem;
}

.quiz-progress-track {
  height: 8px;
  overflow: hidden;
  margin-bottom: 1.35rem;
  border-radius: 999px;
  background: var(--bg-tertiary);
}

.quiz-progress-bar {
  width: 0;
  height: 100%;
  border-radius: inherit;
  background: linear-gradient(90deg, var(--primary-500), #6366f1);
  transition: width 240ms ease;
}

.quiz-question {
  margin: 0 0 1rem;
  font-size: clamp(1.25rem, 3vw, 1.65rem);
  line-height: 1.35;
}

.quiz-options {
  display: grid;
  gap: 0.7rem;
}

.quiz-option {
  width: 100%;
  padding: 0.9rem 1rem;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  background: var(--bg-primary);
  color: var(--text-primary);
  font: inherit;
  line-height: 1.45;
  text-align: left;
  cursor: pointer;
  transition: border-color var(--transition), background var(--transition), transform var(--transition);
}

.quiz-option:hover:not(:disabled),
.quiz-option:focus-visible:not(:disabled) {
  border-color: var(--primary-500);
  transform: translateY(-1px);
}

.quiz-option.correct {
  border-color: #16a34a;
  background: rgba(22, 163, 74, 0.12);
}

.quiz-option.incorrect {
  border-color: #dc2626;
  background: rgba(220, 38, 38, 0.1);
}

.quiz-feedback {
  margin-top: 1rem;
  padding: 1rem;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  background: var(--bg-primary);
}

.quiz-feedback h3 {
  margin: 0 0 0.4rem;
}

.quiz-feedback p {
  margin: 0;
  color: var(--text-secondary);
  line-height: 1.6;
}

.quiz-source {
  display: inline-block;
  margin-top: 0.65rem;
  color: var(--primary-500);
  font-size: 0.78rem;
}

.quiz-result-score {
  margin: 0.5rem 0;
  color: var(--primary-600);
  font-size: clamp(2.5rem, 8vw, 4.5rem);
  font-weight: 850;
  line-height: 1;
}

.quiz-result-copy {
  color: var(--text-secondary);
  line-height: 1.65;
}

.quiz-review {
  display: grid;
  gap: 0.75rem;
  margin-top: 1.25rem;
}

.quiz-review-item {
  padding: 0.9rem;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  background: var(--bg-primary);
}

.quiz-review-item strong,
.quiz-review-item span {
  display: block;
}

.quiz-review-item span {
  margin-top: 0.3rem;
  color: var(--text-secondary);
  font-size: 0.86rem;
}

.android-learning-card {
  margin-top: 1.5rem;
  padding: 1.1rem;
  border: 1px solid rgba(15, 185, 163, 0.32);
  border-radius: var(--radius-lg);
  background: linear-gradient(135deg, rgba(15, 185, 163, 0.12), rgba(99, 102, 241, 0.1));
}

.android-learning-card h2 {
  margin: 0 0 0.4rem;
  font-size: 1.15rem;
}

.android-learning-card p {
  margin: 0;
  color: var(--text-secondary);
  line-height: 1.55;
}

.android-learning-card .learning-actions {
  margin-top: 0.8rem;
}

.learning-disclosure {
  margin-top: 1rem;
  color: var(--text-tertiary);
  font-size: 0.78rem;
  line-height: 1.55;
}

.is-hidden {
  display: none !important;
}

@media (max-width: 820px) {
  .learning-grid,
  .learning-progress {
    grid-template-columns: 1fr;
  }

  .lesson-layout {
    grid-template-columns: 1fr;
  }

  .lesson-nav {
    position: static;
    order: -1;
  }
}

@media (max-width: 560px) {
  .learning-shell {
    padding-inline: 0.75rem;
  }

  .learning-hero,
  .quiz-card,
  .lesson-article {
    border-radius: var(--radius-lg);
  }

  .learning-actions {
    flex-direction: column;
  }

  .learning-button {
    width: 100%;
  }
}

@media (prefers-reduced-motion: reduce) {
  .learning-button,
  .quiz-option,
  .quiz-progress-bar {
    transition: none;
  }
}