body { margin: 0; background: var(--mist-050); color: var(--neutral-900); font-family: system-ui, sans-serif; }
main { max-width: 1720px; margin: auto; padding: 10px 3vw 14px; }
.chapter-context { margin: 0; font-size: 16px; }
#chapter-title { font-size: 22px; margin: 2px 0 8px; }
.section-picker { display: flex; align-items: center; gap: 12px; font-size: 16px; }
select, button { font: inherit; }
select { color: var(--neutral-900); background: white; border: 2px solid var(--mist-400); border-radius: 10px; padding: 10px; min-height: 48px; max-width: 100%; }
#chapter-status:empty { display: none; }
#page-content { min-height: calc(100dvh - 300px); padding: 12px 0; font-size: clamp(22px, 1.7vw, 30px); }
#page-content h2 { font-size: clamp(30px, 2.5vw, 44px); line-height: 1.12; margin: 4px 0 14px; }
#page-content p { margin: 10px 0; }
[hidden] { display: none !important; }
button { touch-action: manipulation; }
button, summary, a { -webkit-tap-highlight-color: transparent; }
.scene-grid, .card-grid, .video-grid, .prehistory-grid { display: grid; gap: 16px; }
.scene-grid { grid-template-columns: repeat(4, minmax(0, 1fr)); grid-template-rows: repeat(2, minmax(180px, 25vh)); }
.card-grid, .prehistory-grid { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.video-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); grid-auto-rows: 25vh; }
.image-tile, .video-tile { position: relative; min-width: 0; min-height: 0; }
.image-view { position: relative; height: 100%; min-height: 120px; overflow: hidden; background: var(--gold-100); border-radius: 14px; }
.image-view img { display: block; width: 100%; height: 100%; object-fit: cover; }
.image-open, .video-open { display: block; width: 100%; height: 100%; padding: 0; border: 2px solid var(--mist-400); border-radius: 16px; overflow: hidden; background: var(--blue-100); color: var(--neutral-900); cursor: pointer; }
.media-placeholder { height: 100%; min-height: 120px; box-sizing: border-box; display: flex; align-items: center; justify-content: center; flex-direction: column; gap: 8px; background: linear-gradient(145deg, var(--gold-100), var(--mist-200)); color: var(--neutral-500); }
.scene-symbol { font-size: 56px; line-height: 1.1; }
#page-content small { font-size: 17px; }
.prompt { font-weight: 700; }
.instruction { font-size: clamp(20px, 1.4vw, 25px); }
.source-button { display: inline-flex; align-items: center; justify-content: center; width: 17.92px; height: 17.92px; min-height: 17.92px; padding: 0; border-radius: 50%; border: 0; background: var(--blue-300); color: white; font-size: 12.32px; line-height: 1; cursor: pointer; }
.image-tile > .source-button, .video-tile > .source-button { position: absolute; bottom: 10px; right: 10px; }
.function-card { min-height: 265px; padding: 20px; text-align: left; border: 2px solid var(--blue-600); border-radius: 18px; color: var(--neutral-900); background: color-mix(in srgb, var(--blue-100) 40%, white); cursor: pointer; font-size: 27px; line-height: 1.18; }
.function-card[aria-expanded="true"] { background: var(--blue-100); }
.card-symbol { display: inline-block; font-size: 36px; margin-right: 12px; color: var(--blue-900); }
.card-explanation { display: block; font-size: 23px; line-height: 1.25; margin-top: 14px; }
.video-open { display: flex; justify-content: center; align-items: center; flex-direction: column; gap: 20px; padding: 24px 64px; }
.play-symbol { font-size: 64px; }
.prehistory-card { position: relative; border: 1px solid var(--mist-400); border-radius: 14px; overflow: hidden; padding: 0 16px 12px; background: white; }
.prehistory-card .image-view { height: 80px; min-height: 0; margin: 0 -16px 8px; border-radius: 0; }
.prehistory-card .media-placeholder { min-height: 0; }
.prehistory-card .scene-symbol { font-size: 36px; }
.prehistory-card .media-placeholder small { font-size: 14px !important; }
.prehistory-card h3 { font-size: 23px; margin: 5px 0; }
.prehistory-card p { font-size: 21px; line-height: 1.2; }
.prehistory-card .source-button { position: absolute; top: auto; left: auto; right: 4px; bottom: 4px; z-index: 1; }
.science-note { margin-top: 12px; padding: 8px 16px; background: var(--green-100); border-radius: 12px; font-size: 23px; }
.science-note p { font-weight: 650; }
.reveal-button, #page-navigation button, .discovery-questions > button, .history-window button:not(.source-button), .science-note button { min-height: 52px; padding: 9px 18px; border: 2px solid var(--blue-900); border-radius: 10px; color: var(--neutral-900); background: white; cursor: pointer; }
.answer { padding: 14px; background: var(--green-100); border-radius: 12px; font-size: 23px; margin: 12px 0; }
.discovery-layout { display: grid; grid-template-columns: 1.1fr 1fr; gap: 24px; min-height: 460px; }
.discovery-layout .image-view img { object-fit: contain; }
.discovery-questions { font-size: 25px; }
.discovery-questions > button { margin: 8px 8px 0 0; }
.discovery-closing { font-size: 26px; }
#page-navigation { display: flex; justify-content: space-between; align-items: center; gap: 20px; font-size: 22px; padding-top: 10px; border-top: 1px solid var(--mist-400); }
#page-navigation button { min-width: 120px; }
button:disabled { opacity: .45; cursor: default; }
button:focus-visible, select:focus-visible, summary:focus-visible, a:focus-visible { outline: 4px solid var(--gold-500); outline-offset: -4px; }
/* Content uses the shared movable/resizable app window lifecycle. Only windows scroll. */
.history-window { position: fixed; left: 5vw; top: 8vh; width: 90vw; height: 82vh; box-sizing: border-box; padding: 24px 30px; background: var(--mist-050); color: var(--neutral-900); overflow: auto; font-size: 26px; }
.history-window h2 { font-size: 34px; line-height: 1.15; margin: 4px 160px 20px 0; }
.history-window h3 { font-size: 27px; }
.history-window .window-close { float: right; position: sticky; top: 0; z-index: 2; }
.history-window p { margin: 14px 0; }
.history-window a { display: inline-block; color: var(--blue-900); min-height: 48px; padding: 8px; box-sizing: border-box; }
.history-window .image-view { height: 57vh; }
.history-window .image-view img { object-fit: contain; }
.history-window .image-tile { height: 280px; margin: 12px 0; }
.history-window .image-tile .image-view { height: 100%; }
.history-window .knowledge-button { margin: 8px 12px 8px 0; }
.video-content { display: grid; grid-template-columns: 1.25fr 1fr; gap: 26px; }
.player-view iframe, .player-view video { width: 100%; aspect-ratio: 16 / 9; border: 0; background: var(--neutral-900); }
.player-view audio { display: block; width: 100%; margin: 16px 0; }
.observations ul { padding-left: 28px; }
.observations li { margin: 12px 0; }
.history-window summary { min-height: 52px; cursor: pointer; background: var(--blue-100); border-radius: 10px; padding: 10px 16px; box-sizing: border-box; }
.future-chapter, .inline-credit { font-size: 21px; }
.source-details p { overflow-wrap: anywhere; }
body .mp-window-bar button { min-width: 48px; min-height: 40px; }
@media (max-width: 1100px) { .scene-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); grid-template-rows: none; grid-auto-rows: 200px; } .card-grid, .prehistory-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); } .video-content { grid-template-columns: 1fr; } .function-card { font-size: 24px; } }
@media (max-width: 650px) { .card-grid, .prehistory-grid, .video-grid, .discovery-layout { grid-template-columns: 1fr; } .section-picker { align-items: start; flex-direction: column; } .discovery-layout > .image-tile { height: 280px; } .history-window { padding: 16px; font-size: 22px; } }
.science-note summary { min-height: 48px; cursor: pointer; padding: 8px; box-sizing: border-box; }
.science-note details p { font-size: 20px; font-weight: 400; line-height: 1.2; }
[data-layout="prehistory"]:has(details[open]) .prehistory-card .image-view { height: 38px; }
[data-layout="prehistory"]:has(details[open]) .prehistory-card .scene-symbol { display: none; }
.image-tile.has-credit .image-open { height: calc(100% - 64px); }
.image-tile.has-credit > .source-button { bottom: 74px; }
.image-tile.has-credit .inline-credit { margin: 4px 0; font-size: 18px; }
/* Scene crops stay legible beside the unchanged hypotheses. */
.prehistory-card { display: grid; grid-template-columns: 40% minmax(0, 1fr); grid-template-rows: auto 1fr; gap: 0 12px; padding: 0; }
.prehistory-card .image-view,
[data-layout="prehistory"]:has(details[open]) .prehistory-card .image-view { grid-column: 1; grid-row: 1 / 3; height: 100%; min-height: 180px; margin: 0; }
.prehistory-card h3 { grid-column: 2; margin: 12px 12px 0 0; }
.prehistory-card p { grid-column: 2; margin: 8px 12px 30px 0 !important; }
@media (min-width: 1101px) {
  [data-layout="prehistory"]:has(details[open]) .prehistory-card { grid-template-columns: 28% minmax(0, 1fr); }
  [data-layout="prehistory"]:has(details[open]) .prehistory-card .image-view { min-height: 140px; }
  [data-layout="prehistory"]:has(details[open]) .prehistory-card h3 { font-size: 21px; }
  [data-layout="prehistory"]:has(details[open]) .prehistory-card p { font-size: 19px; }
}
/* Section documents live in the shared header, outside presentation pages. */
.history-document-buttons { display: flex; align-items: center; gap: 8px; }
.history-document-buttons button { min-height: 44px; padding: 8px 12px; border: 1px solid var(--mist-400); border-radius: 8px; background: var(--blue-900); color: white; font: 14px/1.2 system-ui, sans-serif; white-space: nowrap; cursor: pointer; }
.history-document-buttons button:disabled { cursor: default; }
.history-document-buttons button:not(:disabled):hover { background: var(--blue-600); }
.history-window.history-pdf-window { left: 12vw; top: 12vh; width: min(760px, 90vw); height: min(660px, 72vh); padding: 12px; display: flex; flex-direction: column; gap: 8px; }
.history-pdf-window h2 { font-size: 24px; margin: 0; }
.history-pdf-window > .window-close { position: absolute; right: 12px; top: 8px; min-height: 44px !important; padding: 6px 12px !important; font-size: 16px; }
.pdf-content { display: flex; flex-direction: column; flex: 1; min-height: 0; gap: 8px; }
.pdf-toolbar { display: flex; align-items: center; flex-wrap: wrap; gap: 8px; padding-top: 8px; font-size: 16px; }
.history-pdf-window .pdf-toolbar :is(button, a) { min-height: 44px; box-sizing: border-box; padding: 8px 12px; font: inherit; }
.pdf-toolbar .ui-btn { display: inline-flex; align-items: center; border: 1px solid var(--blue-900); border-radius: 8px; background: white; color: var(--blue-900); text-decoration: none; }
.pdf-viewer { flex: 1; min-height: 0; width: 100%; border: 1px solid var(--mist-400); background: white; }
.history-pdf-window .pdf-print-hint { font-size: 16px; margin: 0; }

/* Only the opening activity uses two-sided picture cards. */
.scene-grid:has(.scene-flip-tile) { grid-template-rows: none; grid-auto-rows: auto; align-items: stretch; }
.scene-flip-tile { position: relative; min-width: 0; perspective: 1200px; }
.scene-flip-card { display: block; width: 100%; height: 100%; padding: 0; border: 2px solid var(--mist-400); border-radius: 16px; background: transparent; color: var(--neutral-900); text-align: left; cursor: pointer; }
.scene-flip-card:focus-visible { outline: 3px solid var(--blue-600); outline-offset: 4px; }
.scene-flip-inner { display: grid; height: 100%; min-height: clamp(230px, 27vh, 300px); transform-style: preserve-3d; transition: transform .45s ease; }
.scene-flip-card.is-flipped .scene-flip-inner { transform: rotateY(180deg); }
.scene-flip-face { grid-area: 1 / 1; border-radius: 14px; backface-visibility: hidden; -webkit-backface-visibility: hidden; }
.scene-flip-front { position: relative; transform: rotateY(0deg); }
.scene-flip-front .image-view { position: absolute; inset: 0; }
.scene-letter { position: absolute; top: 10px; left: 10px; padding: 4px 10px; border-radius: 8px; background: var(--blue-900); color: white; font-size: 22px; font-weight: 700; }
.scene-flip-back { display: flex; flex-direction: column; justify-content: center; gap: 12px; padding: 20px 20px 38px; box-sizing: border-box; background: var(--blue-100); transform: rotateY(180deg); font-size: clamp(20px, 1.5vw, 25px); line-height: 1.3; }
.scene-back-letter { color: var(--blue-900); font-size: 26px; }
.scene-flip-tile > .source-button { position: absolute; bottom: 10px; right: 10px; z-index: 1; }
@media (max-width: 650px) {
  .scene-grid:has(.scene-flip-tile) { grid-template-columns: 1fr; }
}
@media (prefers-reduced-motion: reduce) {
  .scene-flip-inner { transition: none; }
}