/* Mobile reading layer. All rules are scoped below 768px; desktop styles remain untouched. */
@media (max-width: 767px) {
  .page {
    width: 100%;
    max-width: 100%;
    min-width: 0;
    padding: 30px clamp(12px, 4vw, 16px) calc(154px + env(safe-area-inset-bottom));
  }

  .page h1,
  .page h2,
  .page h3,
  .page p,
  .page li,
  .page label,
  .page summary,
  .page a,
  .page strong,
  .page span,
  .page small,
  .page code {
    min-width: 0;
    overflow-wrap: anywhere;
  }

  .page h1 { font-size: clamp(2rem, 8vw, 2.5rem); line-height: 1.18; letter-spacing: -.04em; }
  .page h2 { font-size: clamp(1.5rem, 6vw, 1.85rem); line-height: 1.25; }
  .page h3 { font-size: 1.2rem; line-height: 1.4; }
  .page p,
  .guided-main p,
  .story-card p,
  .archive-record p,
  .feedback,
  .answer,
  .exhibit-body,
  .hall-entry p,
  .hall-experience p,
  .hall-transition p,
  .hall-exhibit-card p,
  .technology-note p,
  .quiz-review p {
    font-size: 1rem;
    line-height: 1.75;
  }

  .page .muted,
  .guided-node-kicker,
  .guided-restore-note,
  .archive-readiness,
  .knowledge-result-context,
  .technical-source-links {
    font-size: .9rem;
    line-height: 1.65;
  }

  .hero,
  .chapter-head,
  .prologue-grid {
    min-width: 0;
    grid-template-columns: minmax(0, 1fr);
  }

  .hero-copy,
  .hero-art,
  .chapter-head > *,
  .prologue-grid > * {
    min-width: 0;
    max-width: 100%;
  }

  .hero-art { overflow: hidden; }
  .home-primary-actions { align-items: stretch; flex-direction: column; }
  .home-primary-actions .btn { width: 100%; min-height: 48px; }

  .grid { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 12px; }
  .options,
  .story-grid,
  .technology-note-grid,
  .hall-exhibit-grid,
  .archive-exhibit-grid,
  .media-grid,
  .archive-return-actions {
    grid-template-columns: minmax(0, 1fr);
  }

  .card,
  .task-panel,
  .story-card,
  .archive-record,
  .archive-source-card,
  .archive-voice-summary,
  .evidence-card,
  .hall-entry,
  .hall-experience,
  .hall-transition,
  .hall-exhibit-card,
  .technology-note,
  .guided-section,
  .guided-locked-note,
  .guided-unlocked-note,
  .guided-original,
  .quiz-perfect,
  .quiz-review article,
  .knowledge-result-context {
    min-width: 0;
    max-width: 100%;
    overflow-wrap: anywhere;
  }

  .task-panel,
  .story-card,
  .archive-record,
  .archive-source-card,
  .archive-voice-summary,
  .evidence-card,
  .hall-entry,
  .hall-experience,
  .hall-transition,
  .hall-exhibit-card,
  .technology-note,
  .guided-section,
  .guided-original,
  .quiz-perfect,
  .quiz-review article {
    padding: 16px;
  }

  .option,
  .quiz-option {
    min-width: 0;
    min-height: 64px;
    padding: 14px;
    font-size: 1rem;
    line-height: 1.65;
    overflow-wrap: anywhere;
  }

  .section-head,
  .media-heading,
  .hall-zone-heading {
    min-width: 0;
    align-items: flex-start;
    flex-direction: column;
    gap: 10px;
  }

  .route-summary { align-items: stretch; flex-direction: column; gap: 10px; }
  .record-row,
  .quiz-record { min-width: 0; grid-template-columns: minmax(0, 1fr); gap: 7px; }
  .record-row > *,
  .quiz-record > * { min-width: 0; grid-column: 1; overflow-wrap: anywhere; }
  .quiz-record button { min-width: 44px; min-height: 44px; justify-self: start; }
  .final-achievement-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 9px; }

  .guided-page { padding: 22px clamp(12px, 4vw, 16px) calc(154px + env(safe-area-inset-bottom)); }
  .guided-head { display: block; }
  .guided-head > .btn { margin: 8px 0; }
  .guided-layout { min-width: 0; grid-template-columns: minmax(0, 1fr); gap: 11px; }
  .guided-rail { position: static; min-width: 0; padding: 12px; }
  .guided-era-list { grid-template-columns: repeat(6, minmax(0, 1fr)); gap: 5px; }
  .guided-era-button { display: grid; justify-items: center; gap: 3px; min-width: 0; min-height: 48px; padding: 6px 2px; }
  .guided-era-button small { margin: 0; font-size: .68rem; }
  .guided-node-list { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 7px; }
  .guided-node-button { min-width: 0; min-height: 44px; padding: 8px; font-size: .875rem; line-height: 1.4; }
  .guided-main { min-width: 0; min-height: 0; padding: 17px 14px; }
  .guided-lan-slot { min-width: 0; padding: 8px; }
  .guided-main .options { grid-template-columns: minmax(0, 1fr); }
  .guided-main .guided-actions .btn,
  .guided-footer-actions .btn { flex: 1 1 100%; min-height: 44px; }

  .chapter-step-navigation { align-items: stretch; flex-direction: column-reverse; gap: 12px; }
  .chapter-step-next { align-items: stretch; flex-direction: column-reverse; gap: 8px; }
  .chapter-step-status { text-align: left; }
  .chapter-step-navigation .btn { width: 100%; min-height: 48px; }

  .history-media,
  .media-grid,
  .media-figure,
  .exhibit-body,
  .exhibit-content { min-width: 0; max-width: 100%; }
  .history-media { padding: 14px; }
  .media-figure > img,
  .exhibit-image {
    display: block;
    width: 100%;
    max-width: 100%;
    height: auto;
    max-height: 58vh;
    max-height: min(58dvh, 460px);
    object-fit: contain;
  }
  .media-figure figcaption,
  .exhibit-caption,
  .thumbnail-caption,
  .thumbnail-meta { min-width: 0; font-size: .875rem; line-height: 1.6; overflow-wrap: anywhere; }
  .media-figure figcaption { padding: 12px; }
  .exhibit-tabs { gap: 6px; }
  .exhibit-tab { min-width: 0; min-height: 44px; padding: 8px 6px; font-size: .875rem; overflow-wrap: anywhere; }
  .exhibit-controls { display: grid; grid-template-columns: minmax(0, 1fr); }
  .exhibit-controls .btn,
  .task-reference .btn { width: 100%; min-height: 44px; }
  .exhibit-thumbnail { min-width: 0; max-width: 100%; }
  .exhibit-thumbnail img { max-width: 100%; object-fit: contain; }
  .image-viewer { padding: calc(12px + env(safe-area-inset-top)) 10px calc(12px + env(safe-area-inset-bottom)); }
  .image-viewer img { width: auto; max-width: 100%; max-height: 82dvh; object-fit: contain; }

  .modal-backdrop,
  .demo-route-backdrop { padding: env(safe-area-inset-top) 0 0; }
  .modal,
  .demo-route-modal {
    width: 100%;
    max-width: 100%;
    max-height: calc(100vh - 8px);
    max-height: calc(100dvh - env(safe-area-inset-top) - env(safe-area-inset-bottom) - 8px);
    margin: 0 auto 0;
    padding: 16px 14px calc(18px + env(safe-area-inset-bottom));
    border-radius: 16px 16px 0 0;
    overflow-x: hidden;
    overflow-y: auto;
    overscroll-behavior: contain;
  }
  .modal-head { min-width: 0; align-items: flex-start; gap: 10px; }
  .modal-head > * { min-width: 0; overflow-wrap: anywhere; }
  .demo-route-mode-grid { grid-template-columns: minmax(0, 1fr); }
  .demo-route-choices { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .demo-route-close { min-width: 44px; min-height: 44px; }
  .health-panel {
    top: auto;
    right: 12px;
    bottom: calc(12px + env(safe-area-inset-bottom));
    width: calc(100vw - 24px);
    max-height: 72vh;
    max-height: min(72dvh, 680px);
    overflow-x: hidden;
    overflow-y: auto;
    overflow-wrap: anywhere;
  }

  .btn,
  .quiet,
  .close,
  .topbar nav button,
  .exhibit-tab,
  .guided-era-button,
  .guided-node-button,
  .quiz-option,
  .image-viewer button,
  .health-close,
  .lan-companion[data-mode="dialogue"] .lan-actions button,
  .lan-companion[data-mode="history"] .lan-history-controls button {
    min-height: 44px;
    touch-action: manipulation;
  }
  .topbar nav button { padding-inline: 9px; }
  input,
  textarea,
  select { max-width: 100%; font-size: 16px; }

  #lanCompanion[data-mode="dialogue"],
  #lanCompanion[data-mode="history"] {
    left: 50%;
    top: 50%;
    top: calc(50% + (env(safe-area-inset-top) - env(safe-area-inset-bottom)) / 2);
    right: auto;
    bottom: auto;
    width: calc(100vw - 24px);
    width: calc(100vw - env(safe-area-inset-left) - env(safe-area-inset-right) - 24px);
    max-width: 760px;
    max-height: calc(100vh - 24px);
    max-height: calc(100dvh - env(safe-area-inset-top) - env(safe-area-inset-bottom) - 24px);
    padding: clamp(14px, 4vw, 18px);
    border-radius: 16px;
    overflow-x: hidden;
    overflow-y: auto;
    overscroll-behavior: contain;
  }
  #lanCompanion[data-mode="dialogue"] .lan-head { gap: 9px; }
  #lanCompanion[data-mode="dialogue"] .lan-portrait { width: 48px; height: 48px; flex-basis: 48px; }
  #lanCompanion[data-mode="dialogue"] .lan-caption {
    max-height: 40vh;
    max-height: min(40dvh, 320px);
    margin: 12px 0;
    padding: 14px;
    font-size: clamp(1rem, 4.2vw, 1.08rem);
    line-height: 1.75;
    overflow-x: hidden;
    overflow-y: auto;
    overflow-wrap: anywhere;
  }
  #lanCompanion[data-mode="dialogue"] .lan-actions { justify-content: stretch; gap: 8px; flex-wrap: wrap; }
  #lanCompanion[data-mode="dialogue"] .lan-actions button { flex: 1 1 auto; min-width: 0; }
  #lanCompanion[data-mode="dialogue"] .lan-footnote { font-size: .875rem; line-height: 1.5; }
  #lanCompanion[data-mode="history"] .lan-history-reader blockquote { font-size: 1rem; line-height: 1.75; }

  #lanCompanion[data-mode="companion"] {
    left: auto;
    right: 10px;
    bottom: calc(10px + env(safe-area-inset-bottom));
    width: min(380px, calc(100vw - 20px));
    height: auto;
    min-height: 136px;
    max-height: min(30dvh, 184px);
    padding: 8px 10px;
    overflow-x: hidden;
    overflow-y: auto;
  }
  #lanCompanion[data-mode="companion"] .lan-caption { font-size: .875rem; line-height: 1.45; }
  #lanCompanion[data-mode="companion"] .lan-actions .lan-skip { min-width: 44px; min-height: 44px; font-size: .75rem; }
  .chapter-step-next>.btn{box-sizing:border-box;flex:0 1 auto;width:100%;min-width:0;max-width:100%;min-height:48px;padding-inline:14px;white-space:normal;overflow:visible;overflow-wrap:anywhere;line-height:1.35}
  .sixg-research-check-list{grid-template-columns:minmax(0,1fr)}
  .sixg-research-check{width:100%;min-height:0}
  .sixg-research-check small{font-size:.9rem}

  /* Collapse the five desktop destinations into an explicit, keyboard-operable menu. */
  #mobileNavToggle {
    display: inline-flex;
    flex: 0 0 auto;
    align-items: center;
    justify-content: center;
    min-width: 44px;
    min-height: 44px;
    padding: 8px 12px;
    border: 1px solid #7996bd4d;
    border-radius: 9px;
    background: #112139a8;
    color: var(--text);
    font-size: 16px;
    cursor: pointer;
  }
  .topbar {
    height: auto;
    min-height: 68px;
    flex-wrap: wrap;
    gap: 8px 12px;
    padding: 10px clamp(12px, 4vw, 16px);
  }
  .brand { min-width: 0; flex: 1 1 0; white-space: normal; }
  .brand > span:last-child { min-width: 0; font-size: 15px; line-height: 1.3; }
  .topbar nav,
  .topbar nav.is-open {
    min-width: 0;
    flex: 1 0 100%;
    order: 3;
    overflow: visible;
  }
  .topbar nav:not(.is-open) { display: none; }
  .topbar nav.is-open { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 7px; }
  .topbar nav button {
    min-width: 0;
    min-height: 48px;
    padding: 8px;
    font-size: 16px;
    line-height: 1.35;
    white-space: normal;
    overflow-wrap: anywhere;
  }
  .topbar nav button:last-child { grid-column: 1 / -1; }
  .page p,
  .page li,
  .page .lead,
  .guided-main p,
  .story-card p,
  .archive-record p,
  .feedback,
  .answer,
  .exhibit-body,
  .knowledge-result p { font-size: 16px; }
  .page .muted,
  .knowledge-result-meta,
  .knowledge-match-reason { font-size: 14px; }
  .knowledge-search-input-row { display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: 8px; }
  .knowledge-search-input-row input,
  .knowledge-search-input-row .btn { min-width: 0; min-height: 48px; }
  .knowledge-suggestions { display: flex; flex-wrap: wrap; gap: 8px; }
  .knowledge-suggestion { min-height: 44px; max-width: 100%; padding: 9px 12px; font-size: 15px; }
  .knowledge-pagination { display: grid; grid-template-columns: minmax(0, 1fr) auto minmax(0, 1fr); gap: 7px; align-items: center; }
  .knowledge-pagination > .btn { min-width: 0; min-height: 44px; padding: 8px; white-space: normal; }
  .knowledge-page-list { grid-column: 1 / -1; grid-row: 2; display: flex; flex-wrap: wrap; justify-content: center; align-items: center; gap: 4px; }
  .knowledge-page-status { grid-column: 2; grid-row: 1; text-align: center; white-space: nowrap; font-size: 14px; }
}

@media (max-width: 560px) {
  .grid,
  .final-achievement-grid { grid-template-columns: minmax(0, 1fr); }
}

@media (max-width: 430px) {
  .final-achievement-grid { grid-template-columns: minmax(0, 1fr); }
  .home-page .hero-art { max-width: 100%; }
  .brand small { display: none; }
  .guided-rail { padding: 10px; }
  .guided-node-list { grid-template-columns: minmax(0, 1fr); }
  .guided-node-button { font-size: .9rem; }
  .history-media { padding: 12px; }
  .modal,
  .demo-route-modal { padding-inline: 12px; }
  .knowledge-search-input-row { grid-template-columns: minmax(0, 1fr); }
  .knowledge-search-input-row .btn { width: 100%; }
}