@media (max-width: 1024px) {
  .nav-shell {
    align-items: stretch;
    flex-direction: column;
  }

  .sticky-nav ul {
    width: 100%;
    overflow-x: auto;
    flex-wrap: nowrap;
    white-space: nowrap;
    padding-bottom: 0.2rem;
    scrollbar-width: thin;
  }

  .sticky-nav li {
    flex: 0 0 auto;
  }

  #revision-mode-toggle {
    align-self: flex-start;
  }

  .lecture-grid,
  .mistakes-grid,
  .cheat-sheet-grid,
  .visualizer-grid,
  .pdf-grid,
  .final-questions-grid,
  .other-results-grid {
    grid-template-columns: 1fr;
  }

  .step-card,
  .example-step {
    grid-template-columns: 52px 1fr;
  }
}

@media (min-width: 641px) and (max-width: 1024px) {
  .lecture-grid {
    grid-template-columns: 1fr;
  }

  .topic-grid,
  .example-steps,
  .command-list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .key-idea-list,
  .mistakes-inline,
  .question-list {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 640px) {
  .container {
    width: min(100% - 1rem, 100%);
  }

  .hero {
    padding-top: 1rem;
  }

  .hero .container {
    padding: 1.35rem;
    border-radius: 26px;
  }

  .hero h1 {
    font-size: clamp(1.95rem, 10vw, 2.8rem);
    max-width: none;
  }

  .hero-copy {
    font-size: 0.98rem;
  }

  .study-path-card {
    padding: 1rem;
  }

  .study-path-item {
    padding: 0.85rem 0.9rem;
  }

  .sticky-nav {
    position: sticky;
  }

  .sticky-nav a {
    min-height: 2.45rem;
    padding: 0.58rem 0.85rem;
    font-size: 0.92rem;
  }

  main {
    padding-top: 1.1rem;
  }

  section {
    margin-top: 1.6rem;
    scroll-margin-top: 5rem;
  }

  .dashboard-intro,
  .section-heading {
    gap: 1rem;
    margin-bottom: 1rem;
  }

  .dashboard-stats,
  .exam-summary-grid,
  .lecture-grid,
  .topic-grid,
  .key-idea-list,
  .mistakes-inline,
  .question-list,
  .question-style-grid,
  .example-steps,
  .command-list,
  .mistakes-grid,
  .labs-grid,
  .cheat-sheet-grid,
  .visualizer-grid,
  .pdf-grid,
  .other-results-grid,
  .exam-mode-grid,
  .final-questions-grid {
    grid-template-columns: 1fr;
  }

  .topic-card,
  .stat-card,
  .comparison-card,
  .mistake-card,
  .viz-card,
  .lab-card,
  #quiz-container,
  .exam-summary-card {
    padding: 1rem;
  }

  .topic-header {
    flex-direction: column;
  }

  .topic-header h3 {
    font-size: 1.28rem;
  }

  .example-step,
  .step-card {
    grid-template-columns: 1fr;
  }

  .example-index,
  .step-number {
    width: 44px;
    height: 44px;
    border-radius: 14px;
  }

  .step-card:not(:last-child)::after {
    display: none;
  }

  .mini-table-row,
  .progress-container,
  .section-title-row,
  .quiz-controls,
  .quick-actions,
  .hero-actions,
  .topic-actions {
    flex-direction: column;
    align-items: stretch;
  }

  .quick-actions .btn,
  .hero-actions .btn,
  .quiz-controls .btn,
  .topic-actions .btn {
    width: 100%;
  }

  .command-tabs {
    flex-wrap: nowrap;
    overflow-x: auto;
    padding-bottom: 0.2rem;
  }

  .tab-btn {
    flex: 0 0 auto;
  }

  .tab-pane {
    grid-template-columns: 1fr;
  }

  .table-responsive {
    margin: 0 -0.15rem;
    padding-bottom: 0.15rem;
  }

  table {
    min-width: 560px;
  }

  .command-block {
    padding: 0.95rem;
  }

  .cmd-line {
    font-size: 0.9rem;
  }

  .viz-card h4 {
    margin-bottom: 0.75rem;
  }

  #quiz-question h3 {
    font-size: 1.15rem;
  }

  .quiz-option {
    min-height: 3.95rem;
    padding: 1rem;
  }

  .pdf-card {
    gap: 0.2rem;
  }
}

@media (max-width: 420px) {
  .container {
    width: min(100% - 0.75rem, 1180px);
  }

  .hero .container {
    padding: 1.1rem;
    border-radius: 22px;
  }

  .hero h1 {
    font-size: 1.8rem;
  }

  .stat-card p,
  .quiz-finish-score {
    font-size: 1.8rem;
  }

  #search-input {
    min-height: 3.2rem;
    padding: 0.9rem 1rem;
  }

  .sticky-nav a {
    padding: 0.55rem 0.8rem;
  }

  table {
    min-width: 500px;
  }
}