/* Quiz + challenge */
  .quiz-center-divider {
    display: none;
    position: absolute;
    left: 50%;
    top: 0;
    bottom: 0;
    width: 0;
    margin: 0;
    padding: 0;
    border: 0;
    pointer-events: none;
    z-index: 20;
  }
  .quiz-panel {
    display: none;
    position: absolute;
    left: var(--quiz-panel-left, 1%);
    top: var(--quiz-panel-top, 1%);
    width: var(--quiz-panel-width, 48%);
    height: var(--quiz-panel-height, 98%);
    box-sizing: border-box;
    border-radius: var(--quiz-panel-radius, calc(var(--sim-panel-radius-pct-h, 2.0619%) * 0.98));
    background: linear-gradient(160deg, rgba(15, 28, 53, 0.94), rgba(7, 16, 32, 0.97));
    border: 1px solid rgba(79, 209, 255, 0.35);
    box-shadow: 0 8px 22px rgba(0, 0, 0, 0.45);
    z-index: 30;
    overflow: hidden;
    pointer-events: auto;
  }
  .quiz-panel-inner {
    height: 100%;
    display: grid;
    grid-template-rows: auto minmax(0, 1fr) minmax(50%, 1fr);
    gap: var(--quiz-panel-gap, 12px);
    padding: var(--quiz-panel-pad, 14px);
    box-sizing: border-box;
  }
  .quiz-panel-actions {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: var(--quiz-panel-action-gap, 8px);
  }
  .quiz-panel-actions.is-challenge-progress {
    grid-template-columns: minmax(0, 2fr) minmax(0, 1fr);
    align-items: stretch;
    border: 1px solid rgba(79, 209, 255, 0.45);
    border-radius: var(--quiz-panel-btn-radius, 8px);
    overflow: hidden;
    background: rgba(15, 24, 57, 0.92);
    min-height: var(--quiz-panel-action-min-height, 64px);
  }
  .quiz-challenge-progress-question {
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 4px 10px;
    font-size: clamp(22px, 4.8vh, 56px);
    font-weight: 900;
    line-height: 1.05;
    color: #eaf2ff;
    text-align: center;
    min-width: 0;
    white-space: nowrap;
  }
  .quiz-challenge-progress-score {
    display: flex;
    flex-direction: column;
    justify-content: center;
    gap: 2px;
    padding: 4px 8px;
    font-size: clamp(14px, 2.6vh, 28px);
    font-weight: 800;
    color: #e6edff;
    line-height: 1.12;
    min-width: 0;
  }
  .quiz-challenge-progress-score.is-blank {
    visibility: hidden;
  }
  .quiz-panel-actions button {
    border-radius: var(--quiz-panel-btn-radius, 8px);
    border: 2px solid rgba(79, 209, 255, 0.35);
    background: rgba(19, 32, 84, 0.92);
    color: #e6edff;
    font-size: var(--quiz-panel-action-font, 18px);
    line-height: 1.15;
    padding: var(--quiz-panel-action-pad-y, 12px) var(--quiz-panel-action-pad-x, 24px);
    min-height: var(--quiz-panel-action-min-height, 64px);
    min-width: 0;
    white-space: normal;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    position: relative;
    overflow: hidden;
  }
  .quiz-panel-actions button.quiz-nav-prev {
    padding-left: var(--quiz-panel-nav-pad, 48px);
  }
  .quiz-panel-actions button.quiz-nav-next {
    padding-right: var(--quiz-panel-nav-pad, 48px);
  }
  .quiz-panel-actions button.quiz-nav-prev::before,
  .quiz-panel-actions button.quiz-nav-next::after {
    position: absolute;
    top: 50%;
    transform: translateY(-50%);
    font-size: var(--quiz-panel-nav-chevron, 48px);
    line-height: 0.8;
    display: flex;
    align-items: center;
    justify-content: center;
    color: rgba(155, 231, 255, 0.95);
    text-shadow: 0 0 12px rgba(79, 209, 255, 0.7);
    pointer-events: none;
  }
  .quiz-panel-actions button.quiz-nav-prev::before {
    content: "\2039";
    left: var(--quiz-panel-nav-inset, 8px);
  }
  .quiz-panel-actions button.quiz-nav-next::after {
    content: "\203A";
    right: var(--quiz-panel-nav-inset, 8px);
  }
  .quiz-question {
    margin: 0;
    color: #f8fbff;
    font-size: var(--quiz-panel-question-font, 36px);
    line-height: 1.12;
    font-weight: 750;
    min-height: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    overflow: hidden;
    white-space: normal;
    overflow-wrap: break-word;
  }
  .quiz-question.is-function-to-name {
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 0.55em;
    text-align: center;
  }
  .quiz-question-text {
    display: block;
    width: 100%;
    max-width: 100%;
    overflow-wrap: break-word;
  }
  .quiz-question-prompt {
    display: block;
    width: 100%;
    text-align: center;
    overflow-wrap: break-word;
  }
  .quiz-question-function {
    display: block;
    width: 100%;
    text-align: center;
    font-weight: 650;
    font-style: italic;
    overflow-wrap: break-word;
  }
  .quiz-answer-area {
    display: grid;
    grid-template-rows: 1fr auto;
    gap: var(--quiz-panel-answer-gap, 10px);
    min-height: 0;
  }
  .quiz-options-grid {
    align-self: stretch;
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    grid-template-rows: repeat(2, minmax(0, 1fr));
    gap: var(--quiz-panel-option-gap, 10px);
    min-height: 0;
    height: 100%;
  }
  .quiz-option-btn {
    border-radius: var(--quiz-panel-btn-radius, 8px);
    border: var(--quiz-panel-option-border, 6px) solid rgba(79, 209, 255, 0.35);
    background: rgba(10, 16, 40, 0.92);
    color: #eaf2ff;
    font-size: var(--quiz-answer-font-size, var(--quiz-panel-option-font, 16px));
    line-height: 1.12;
    padding: var(--quiz-panel-option-pad, 10px);
    min-width: 0;
    white-space: normal;
    overflow-wrap: normal;
    word-break: normal;
    hyphens: none;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    overflow: hidden;
    position: relative;
  }
  .quiz-option-btn:disabled,
  .quiz-panel.is-insufficient .quiz-panel-actions button,
  .quiz-panel.is-insufficient .quiz-option-btn {
    opacity: 0.45;
    cursor: not-allowed;
    filter: grayscale(0.35);
    pointer-events: none;
  }
  /* Challenge: lock further clicks without greying the vibrant correct/incorrect colours. */
  .quiz-option-btn.is-challenge-locked {
    pointer-events: none;
    cursor: default;
  }
  .quiz-panel.is-insufficient .quiz-question {
    color: #9aa8cc;
  }
  .quiz-status.is-insufficient {
    color: #c5d0ef;
    font-weight: 650;
    text-align: center;
    line-height: 1.45;
  }
  .quiz-option-text {
    display: block;
    width: 100%;
    max-width: 100%;
    overflow-wrap: normal;
    word-break: normal;
    hyphens: none;
    position: relative;
    z-index: 1;
  }
  .quiz-option-btn.is-correct::after,
  .quiz-option-btn.is-incorrect::after {
    position: absolute;
    top: var(--quiz-panel-mark-inset, 6px);
    right: var(--quiz-panel-mark-inset-x, 10px);
    z-index: 2;
    pointer-events: none;
    font-family: var(--sans);
    font-size: var(--quiz-panel-mark-font, 48px);
    font-weight: 900;
    line-height: 1;
    text-shadow:
      0 0 2px rgba(255, 255, 255, 0.95),
      0 0 8px rgba(255, 255, 255, 0.55);
  }
  .quiz-option-btn.is-correct::after {
    content: "\2713";
    color: #15803d;
  }
  .quiz-option-btn.is-incorrect::after {
    content: "\2715";
    color: #ff0000;
  }
  .quiz-option-letter {
    color: var(--quiz-letter-color, inherit);
    font-weight: 850;
  }
  .quiz-option-answer {
    color: inherit;
  }
  .quiz-option-btn.has-colored-letter .quiz-option-answer {
    color: #eaf2ff;
  }
  .quiz-option-btn.has-colored-letter.is-correct .quiz-option-letter,
  .quiz-option-btn.has-colored-letter.is-correct .quiz-option-answer {
    color: rgba(34, 197, 94, 0.98);
  }
  .quiz-option-btn.has-colored-letter.is-incorrect .quiz-option-letter,
  .quiz-option-btn.has-colored-letter.is-incorrect .quiz-option-answer {
    color: #ff0000;
  }
  .quiz-option-btn.is-correct {
    border-color: rgba(34, 197, 94, 0.98);
    background: rgb(134, 239, 172);
    color: rgba(34, 197, 94, 0.98);
  }
  .quiz-option-btn.is-incorrect {
    border-color: #ff0000;
    background: rgb(255, 224, 224);
    color: #ff0000;
  }
  .quiz-option-btn.is-correct .quiz-option-text,
  .quiz-option-btn.is-incorrect .quiz-option-text {
    color: inherit;
  }
  .quiz-option-btn.is-find-part-letter {
    font-weight: 800;
    letter-spacing: 0;
    color: var(--quiz-letter-color, #eaf2ff);
    border-color: color-mix(in srgb, var(--quiz-letter-color, #4fd1ff) 70%, #0a1028);
    background: rgba(8, 12, 28, 0.92);
    text-shadow: none;
  }
  .quiz-option-btn.is-find-part-letter .quiz-option-text {
    font-size: 2.7em;
    line-height: 1;
    overflow-wrap: normal;
  }
  .quiz-option-btn.is-find-part-letter.is-correct {
    border-color: rgba(34, 197, 94, 0.95);
    color: var(--quiz-letter-color, #eaf2ff);
    background: rgb(134, 239, 172);
  }
  .quiz-option-btn.is-find-part-letter.is-incorrect {
    border-color: #ff0000;
    color: #ff0000;
    background: rgb(255, 224, 224);
  }
  .quiz-find-part-overlay {
    position: absolute;
    inset: 0;
    pointer-events: none;
    z-index: 6;
    overflow: hidden;
  }
  .quiz-find-part-overlay[hidden] {
    display: none !important;
  }
  .quiz-find-part-svg {
    position: absolute;
    inset: 0;
    width: 100%;
    height: 100%;
    overflow: visible;
  }
  .quiz-find-part-letter {
    position: absolute;
    transform: translate(-50%, -50%);
    font-weight: 800;
    font-family: var(--sans);
    font-size: clamp(36px, 4.8vw, 56px);
    line-height: 1;
    color: var(--quiz-letter-color, #fff);
    text-shadow:
      0 0 10px color-mix(in srgb, var(--quiz-letter-color, #fff) 75%, transparent),
      0 1px 3px rgba(0, 0, 0, 0.9);
    user-select: none;
  }
  .quiz-status {
    color: #9be7ff;
    font-size: var(--quiz-panel-status-font, 13px);
    line-height: 1.35;
  }
  body.app-mode-quiz .quiz-center-divider,
  body.app-mode-quiz .quiz-panel {
    display: block;
  }
  .model-level-select {
    flex: 1 1 220px;
    min-width: 0;
    max-width: 100%;
    padding: 8px 10px;
    border-radius: 8px;
    border: 1px solid rgba(148, 163, 184, 0.35);
    background: rgba(15, 23, 42, 0.55);
    color: #e2e8f0;
    font-size: 13px;
  }
  .model-level-select:focus {
    outline: 2px solid rgba(56, 189, 248, 0.55);
    outline-offset: 1px;
  }
  .click-to-hide-btn {
    margin: 0;
    padding: 8px 12px;
    border-radius: 10px;
    border: 1px solid #22306a;
    background: #132054;
    color: #e6edff;
    font-weight: 700;
    font-family: var(--sans);
    cursor: pointer;
    white-space: nowrap;
    text-align: center;
  }
  .click-to-hide-btn:hover:not(:disabled),
  .click-to-hide-btn:focus-visible:not(:disabled) {
    border-color: rgba(79, 209, 255, 0.45);
    outline: none;
  }
  .click-to-hide-btn:disabled {
    opacity: 0.45;
    cursor: default;
  }
  .click-to-hide-btn.is-hidden {
    display: none;
  }
  .system-bulk-actions {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 0;
    border: 1px solid #22306a;
    border-radius: 10px;
    overflow: hidden;
    width: 100%;
  }
  .system-bulk-btn {
    border: 0;
    border-radius: 0;
    margin: 0;
    background: #132054;
    color: #e6edff;
    font-weight: 700;
    font-family: var(--sans);
  }
  .system-bulk-btn + .system-bulk-btn {
    border-left: 1px solid #22306a;
  }
  .system-bulk-btn:active {
    background: #2563eb;
    color: #ffffff;
  }
  .system-grid {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    grid-template-rows: repeat(4, minmax(0, auto));
    gap: 0;
    width: 100%;
    max-width: 100%;
    border: 1px solid #22306a;
    border-radius: 10px;
    overflow: hidden;
    box-sizing: border-box;
  }
  .system-grid-btn,
  .system-grid-slot {
    min-height: 0;
    margin: 0;
    border: 0;
    border-radius: 0;
    box-shadow: inset -1px 0 0 #22306a, inset 0 -1px 0 #22306a;
    min-width: 0;
  }
  .system-grid-btn {
    padding: 10px 4px;
    background: #0f1839;
    color: #dbe7ff;
    font-weight: 700;
    font-family: var(--sans);
    font-size: 16px;
    line-height: 1.15;
    text-align: center;
    cursor: pointer;
  }
  .settings-panel .system-grid-btn {
    padding: calc(8px * var(--settings-scale)) calc(3px * var(--settings-scale));
    font-size: calc(16px * var(--settings-scale));
  }
  .system-grid-btn.is-on {
    background: #2563eb;
    color: #ffffff;
  }
  .system-grid-btn.is-unavailable {
    background: #151b33;
    color: #6b7280;
    cursor: not-allowed;
    opacity: 0.72;
  }
  .system-grid-btn.is-unavailable.is-on {
    background: #1e293b;
    color: #6b7280;
  }
  .system-grid-slot--empty {
    display: block;
    background: #0a1028;
    pointer-events: none;
  }
  .hidden {
    display: none !important;
  }
  @media (hover: none) and (pointer: coarse) {
    html, body {
      height: auto;
      overflow: visible;
    }
    .app {
      height: 100dvh;
      overflow: hidden;
    }
    .settings-panel {
      --settings-scale: 0.85;
      touch-action: pan-y;
    }
    .settings-panel .system-selection {
      margin: 0;
      padding-left: 0;
      padding-right: 0;
      width: 100%;
      max-width: 100%;
    }
    .settings-panel .system-grid,
    .settings-panel .system-bulk-actions {
      width: 100%;
      max-width: 100%;
    }
    .mode-toggle button {
      white-space: nowrap;
    }
    .instructions-popup {
      width: min(680px, calc(100vw - 24px));
      min-width: 0;
      max-height: calc(100dvh - 80px);
      overflow: auto;
    }
    .browser-panel-stack {
      max-width: min(280px, 70vw);
    }
    .z-anatomy-credit {
      font-size: 8px;
    }
    .z-anatomy-credit-backdrop {
      display: none;
      position: absolute;
      inset: 0;
      z-index: 125;
      margin: 0;
      padding: 0;
      border: 0;
      background: rgba(3, 8, 18, 0.62);
      pointer-events: auto;
      cursor: pointer;
    }
    .simulation-panel.has-z-anatomy-credit-open .z-anatomy-credit-backdrop {
      display: block;
    }
    .simulation-panel.has-z-anatomy-credit-open .z-anatomy-credit {
      left: 8px;
      right: 8px;
      bottom: 8px;
      top: 8px;
      z-index: 130;
      display: flex;
      flex-direction: column;
      justify-content: flex-end;
      align-items: stretch;
      pointer-events: none;
    }
    .simulation-panel.has-z-anatomy-credit-open .z-anatomy-credit-trigger {
      pointer-events: auto;
      align-self: flex-end;
      flex-shrink: 0;
    }
    .simulation-panel.has-z-anatomy-credit-open .z-anatomy-credit-panel {
      position: relative;
      right: auto;
      bottom: auto;
      width: 100%;
      max-width: none;
      max-height: calc(100% - 44px);
      margin: 0 0 8px;
      box-sizing: border-box;
      pointer-events: auto;
      flex: 1 1 auto;
      min-height: 0;
    }
    .simulation-panel.has-z-anatomy-credit-open .z-anatomy-credit-close {
      display: flex;
      align-items: center;
      justify-content: center;
      width: 36px;
      height: 36px;
      font-size: 24px;
      background: rgba(15, 28, 53, 0.95);
      border: 1px solid rgba(79, 209, 255, 0.35);
      border-radius: 6px;
      color: var(--accent-soft);
    }
    .browser-panel-stack:has(.is-mobile-expanded) {
      top: 0;
      left: 0;
      right: 0;
      width: 100%;
      max-width: none;
      height: 100%;
      z-index: 120;
      gap: 0;
    }
    #skeletonBrowserPanel:not(.is-mobile-expanded),
    #anatomySearchPanel:not(.is-mobile-expanded) {
      max-height: none;
      overflow: hidden;
      padding: 3px 8px;
      line-height: 1.15;
    }
    #skeletonBrowserPanel:not(.is-mobile-expanded) .skeleton-browser-panel-header,
    #anatomySearchPanel:not(.is-mobile-expanded) .anatomy-search-header {
      margin-bottom: 0;
      gap: 0;
      align-items: center;
    }
    #skeletonBrowserPanel:not(.is-mobile-expanded) .skeleton-browser-panel-title,
    #anatomySearchPanel:not(.is-mobile-expanded) .skeleton-browser-panel-title {
      font-size: calc(var(--skel-browser-title-size, 12px) * 0.8);
      line-height: 1.15;
    }
    #skeletonBrowserPanel:not(.is-mobile-expanded) .skeleton-browser-panel-bulk,
    #skeletonBrowserPanel:not(.is-mobile-expanded) .browser-panel-body,
    #skeletonBrowserPanel:not(.is-mobile-expanded) .browser-mobile-ok-bar,
    #anatomySearchPanel:not(.is-mobile-expanded) .anatomy-search-header-actions,
    #anatomySearchPanel:not(.is-mobile-expanded) .browser-panel-body,
    #anatomySearchPanel:not(.is-mobile-expanded) .browser-mobile-ok-bar {
      display: none !important;
    }
    #skeletonBrowserPanel.is-mobile-expanded,
    #anatomySearchPanel.is-mobile-expanded {
      position: absolute;
      top: 0;
      left: 0;
      width: 100%;
      max-width: none;
      height: 100dvh;
      max-height: none;
      z-index: 121;
      display: flex;
      flex-direction: column;
      overflow: hidden;
      border-radius: 0;
      padding: 0;
      box-sizing: border-box;
    }
    #skeletonBrowserPanel.is-mobile-expanded .browser-mobile-ok-bar,
    #anatomySearchPanel.is-mobile-expanded .browser-mobile-ok-bar {
      display: flex;
      align-items: center;
      justify-content: flex-end;
      flex-shrink: 0;
      position: sticky;
      top: 0;
      z-index: 2;
      padding: calc(10px * var(--sim-scale, 1)) calc(12px * var(--sim-scale, 1));
      background: rgba(7, 16, 32, 0.98);
      border-bottom: 1px solid rgba(79, 209, 255, 0.28);
    }
    #skeletonBrowserPanel.is-mobile-expanded .skeleton-browser-panel-header,
    #anatomySearchPanel.is-mobile-expanded .anatomy-search-header {
      flex-shrink: 0;
      padding: calc(8px * var(--sim-scale, 1)) calc(12px * var(--sim-scale, 1)) 0;
      margin-bottom: calc(6px * var(--sim-scale, 1));
    }
    #skeletonBrowserPanel.is-mobile-expanded .browser-panel-body,
    #anatomySearchPanel.is-mobile-expanded .browser-panel-body {
      flex: 1 1 auto;
      min-height: 0;
      overflow-x: hidden;
      overflow-y: auto;
      padding: 0 calc(12px * var(--sim-scale, 1)) calc(16px * var(--sim-scale, 1));
      -webkit-overflow-scrolling: touch;
    }
    .skeleton-browser-inline-nest {
      position: relative !important;
      top: auto !important;
      left: auto !important;
      z-index: auto !important;
      max-width: none !important;
      max-height: none !important;
      margin: calc(4px * var(--sim-scale, 1)) 0 calc(6px * var(--sim-scale, 1)) calc(14px * var(--sim-scale, 1));
      padding: calc(6px * var(--sim-scale, 1));
      box-shadow: none;
      border-radius: calc(6px * var(--sim-scale, 1));
      background: rgba(10, 20, 40, 0.88);
    }
    .skeleton-browser-expand.is-open {
      color: var(--accent-soft);
      border-color: rgba(79, 209, 255, 0.55);
    }
    #browserPanelStack:has(#skeletonBrowserPanel.is-mobile-expanded) #anatomySearchPanel:not(.is-mobile-expanded),
    #browserPanelStack:has(#anatomySearchPanel.is-mobile-expanded) #skeletonBrowserPanel:not(.is-mobile-expanded) {
      display: none;
    }
    .skeleton-browser-panel,
    .skeleton-browser-layer,
    .skeleton-browser-inline-nest {
      --sim-scale: 1;
      font-size: var(--skel-browser-font-size, 11px);
    }
  }
  @media (max-aspect-ratio: 1 / 1) and (hover: none) and (pointer: coarse) {
    html, body {
      height: auto;
      overflow-x: hidden;
      overflow-y: auto;
    }
    .app {
      flex-direction: column;
      height: auto;
      min-height: 100dvh;
      overflow: visible;
      padding: 0;
      gap: 0;
      width: 100%;
      max-width: 100%;
      /* Reserve space for the fixed sim chrome so settings scroll underneath it. */
      --mobile-portrait-sim-offset: calc((100vw * 34 / 57) + 16px);
      padding-top: var(--mobile-portrait-sim-offset);
    }
    .simulation-area {
      /* Fixed (not sticky): must stay put while the settings panel scrolls. */
      position: fixed;
      top: 0;
      left: 0;
      right: 0;
      z-index: 60;
      flex: 0 0 auto;
      width: 100%;
      max-width: 100%;
      order: 1;
      align-items: center;
      justify-content: center;
      padding: 8px 0;
      height: var(--mobile-portrait-sim-offset);
      min-height: var(--mobile-portrait-sim-offset);
      box-sizing: border-box;
      background: var(--bg, #071020);
      box-shadow: 0 8px 18px rgba(0, 0, 0, 0.45);
    }
    .simulation-panel {
      width: 100%;
      max-width: 100%;
    }
    .settings-panel {
      flex: 0 0 auto;
      align-self: stretch;
      width: 100%;
      min-width: 0;
      max-width: none;
      order: 2;
      --settings-scale: clamp(0.7, calc(100vw / 535), 0.95);
      overflow-x: hidden;
      overflow-y: visible;
      padding-left: 12px;
      padding-right: 12px;
      border-radius: 0;
      border-left: none;
      border-right: none;
      /* Keep settings panel behind the fixed sim area (z-index 60). */
      position: relative;
      z-index: 50;
    }
    .settings-panel .seg {
      width: max-content;
      max-width: 100%;
    }
    .settings-panel .seg button {
      flex: 0 0 auto;
    }
    .settings-panel .app-mode-control .seg {
      flex: 0 0 auto;
      width: max-content;
      min-width: 0;
      max-width: 100%;
      margin-left: auto;
    }
    .settings-panel .app-mode-control .seg button {
      /* Match On/Off toggle height; extra width so Explore/Quiz fit comfortably */
      padding: 6px 20px;
      font-size: calc(13px * var(--settings-scale, 1));
      line-height: 1.2;
      white-space: nowrap;
    }
    .settings-panel .app-mode-row {
      justify-content: space-between;
      flex-wrap: nowrap;
      align-items: center;
    }
    .settings-panel .app-mode-label {
      flex: 1 1 auto;
      min-width: 0;
    }
    .settings-panel .quiz-type-btn {
      padding-top: 15px;
      padding-bottom: 15px;
    }
    .settings-panel .control-row {
      flex-wrap: wrap;
    }
    .top-buttons {
      gap: clamp(6px, 1.5vw, 10px);
      left: 12px;
      right: 12px;
    }
    .top-buttons .se-button,
    .top-buttons .instructions-button {
      font-size: clamp(10px, 2.6vw, 13px);
      padding: clamp(6px, 1.8vw, 8px) clamp(8px, 2.4vw, 12px);
      white-space: nowrap;
    }
    .settings-panel .se-button .se-icon {
      width: clamp(14px, 3vw, 18px);
      height: clamp(14px, 3vw, 18px);
    }
  }
  @media (min-aspect-ratio: 1 / 1) and (hover: none) and (pointer: coarse) {
    .app {
      padding: 0;
      gap: 0;
    }
    .app {
      flex-direction: row;
    }
    .simulation-area {
      flex: 0 0 66.666%;
      width: 66.666vw;
    }
    .settings-panel {
      flex: 0 0 33.333%;
      width: 33.333vw;
      min-width: 0;
      max-width: 33.333vw;
      --settings-scale: 0.7;
      overflow-x: hidden;
    }
    .top-buttons .se-button,
    .top-buttons .instructions-button {
      font-size: clamp(10px, 1.05vw, 12px);
    }
    .settings-panel .seg {
      width: max-content;
      max-width: 100%;
    }
    .settings-panel .seg button {
      flex: 0 0 auto;
    }
    .settings-panel .app-mode-control .seg {
      flex: 0 0 auto;
      width: max-content;
      min-width: 0;
      max-width: 100%;
    }
    .settings-panel .control-row,
    .settings-panel .app-mode-row,
    .settings-panel .model-level-row,
    .settings-panel .click-to-hide-main-row,
    .settings-panel .deselection-effect-row,
    .settings-panel .quiz-fade-other-row,
    .settings-panel .show-functions-row,
    .settings-panel .modesty-filter-row {
      flex-wrap: wrap;
      justify-content: flex-end;
      align-items: center;
      column-gap: 10px;
      row-gap: 8px;
    }
    /* Keep headings on the left when they share a row; toggles stay right even when wrapped alone. */
    .settings-panel .app-mode-label,
    .settings-panel .model-level-label,
    .settings-panel .click-to-hide-main-row .settings-subheading,
    .settings-panel .deselection-effect-row .settings-subheading,
    .settings-panel .quiz-fade-other-row .settings-subheading,
    .settings-panel .show-functions-row .settings-subheading,
    .settings-panel .modesty-filter-row .settings-subheading,
    .settings-panel .quiz-subsystem-row .settings-subheading {
      margin-right: auto !important;
      flex: 0 1 auto;
      min-width: 0;
    }
    .settings-panel .app-mode-control .seg,
    .settings-panel .model-level-select,
    .settings-panel .click-to-hide-main-controls,
    .settings-panel .deselection-effect-row .seg,
    .settings-panel .quiz-fade-other-row .seg,
    .settings-panel .show-functions-row .seg,
    .settings-panel .modesty-filter-row .seg {
      margin-left: 0 !important;
      margin-right: 0 !important;
      flex: 0 0 auto;
      width: max-content;
      max-width: 100%;
    }
    .browser-panel-stack:has(.is-mobile-expanded) {
      width: 50%;
      max-width: 50%;
      right: auto;
    }
    #skeletonBrowserPanel.is-mobile-expanded,
    #anatomySearchPanel.is-mobile-expanded {
      width: 100%;
      max-width: none;
    }
  }
  .challenge-overlay {
    position: fixed;
    inset: 0;
    background: rgba(3, 8, 18, 0.82);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 5200;
    padding: 20px;
  }
  .challenge-overlay.hidden {
    display: none !important;
  }
  .challenge-window {
    width: min(520px, 100%);
    max-height: min(90dvh, 720px);
    overflow: auto;
    background: linear-gradient(160deg, rgba(12, 20, 38, 0.98), rgba(9, 14, 30, 0.98));
    border: 1px solid rgba(79, 209, 255, 0.55);
    border-radius: 14px;
    box-shadow: 0 0 24px rgba(79, 209, 255, 0.22);
    padding: 18px 18px 16px;
    color: var(--text);
  }
  .challenge-window.is-confirm,
  .challenge-window.is-complete {
    width: min(420px, 100%);
  }
  .challenge-window.is-complete {
    width: min(640px, 100%);
  }
  .challenge-window-title {
    margin: 0 0 14px;
    font-size: 1.25rem;
    font-weight: 800;
    color: var(--accent-soft);
  }
  .challenge-window-subtitle {
    margin: 0 0 8px;
    font-size: 0.95rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    color: var(--accent-soft);
  }
  .challenge-window-section {
    margin-bottom: 14px;
  }
  .challenge-number-input {
    width: 100%;
    max-width: 140px;
    padding: 8px 10px;
    border-radius: 8px;
    border: 1px solid #22306a;
    background: #0f1839;
    color: var(--text);
    font-size: 1rem;
    font-weight: 700;
  }
  .challenge-window-actions {
    display: flex;
    justify-content: flex-end;
    gap: 10px;
    margin-top: 8px;
  }
  .challenge-window-actions button,
  .challenge-complete-close {
    padding: 8px 16px;
    border-radius: 8px;
    border: 1px solid #22306a;
    background: #101a42;
    color: var(--text);
    font-weight: 700;
    cursor: pointer;
  }
  .challenge-window-actions button.challenge-primary,
  .challenge-complete-close {
    background: #2563eb;
    border-color: #4fd1ff;
    color: #fff;
  }
  .challenge-confirm-message {
    margin: 0 0 16px;
    font-size: 1rem;
    line-height: 1.45;
  }
  .challenge-final-score {
    margin: 0 0 16px;
    font-size: 1.2rem;
    font-weight: 800;
    text-align: center;
    color: #9be7ff;
  }
  .challenge-results-columns {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 16px;
    margin-bottom: 16px;
  }
  .challenge-results-column h3 {
    margin: 0 0 8px;
    font-size: 0.95rem;
    font-weight: 800;
    color: var(--accent-soft);
    text-transform: uppercase;
    letter-spacing: 0.4px;
  }
  .challenge-results-column ul {
    margin: 0;
    padding-left: 1.1em;
  }
  .challenge-results-column li {
    margin: 0.35em 0;
    font-size: 0.92rem;
  }
  .challenge-results-empty {
    color: var(--muted);
    font-style: italic;
  }