/* ---------- Home hero ---------- */
.hero { background: var(--navy); color: var(--panel-text); overflow: hidden; }
.hero .grid { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1.1fr); gap: 24px; align-items: center; min-height: 520px; }
.hero h1 { color: #fff; margin-bottom: 14px; }
.hero h1 span { display: block; font-size: .42em; font-stretch: 100%; font-weight: 600; color: var(--panel-dim); letter-spacing: .01em; margin-top: 10px; }
.hero .tagline { font-size: 1.15rem; color: var(--amber-soft); font-weight: 600; margin-bottom: 18px; word-spacing: .2em; }
.hero p.lead { color: var(--panel-text); max-width: 52ch; font-family: var(--font-read); font-size: 1.08rem; }
.hero .actions { display: flex; gap: 10px; flex-wrap: wrap; margin-top: 20px; }
.hero .actions .btn.ghost { color: var(--panel-text); border-color: var(--navy-line); }
.hero-stage { position: relative; height: 500px; }
.hero-stage canvas { display: block; width: 100% !important; height: 100% !important; }
.hero-readout { position: absolute; left: 12px; bottom: 12px; background: rgba(10,22,48,.82); border: 1px solid var(--navy-line); border-radius: var(--radius-m); padding: 10px 12px; font-size: .8rem; color: var(--panel-dim); min-width: 220px; }
.hero-readout b { color: var(--amber); font-weight: 650; }
.hero-readout div { display: flex; justify-content: space-between; gap: 14px; }
.inst-line { font-size: .85rem; color: var(--panel-dim); margin-top: 18px; }
@media (max-width: 900px) {
  .hero .grid { grid-template-columns: 1fr; min-height: 0; padding: 28px 0 10px; }
  .hero-stage { height: 340px; }
}

/* ---------- Unit list (sequence I–IV) ---------- */
.units-list { list-style: none; margin: 36px 0 0; padding: 0; display: grid; gap: 0; border-top: 2px solid var(--ink); }
.unit-row { display: grid; grid-template-columns: 110px minmax(0,1fr) 220px; gap: 24px; padding: 26px 0; border-bottom: 1px solid var(--rule); align-items: start; }
.unit-num { font-size: 3.4rem; font-weight: 800; font-stretch: 125%; line-height: .9; color: var(--ink); }
.unit-row h3 { font-size: 1.35rem; font-stretch: 110%; margin-bottom: 6px; }
.unit-row p { color: var(--ink-2); font-family: var(--font-read); max-width: 70ch; margin-bottom: 10px; }
.unit-topics { display: flex; flex-wrap: wrap; gap: 6px; }
.unit-topics a { font-size: .8rem; text-decoration: none; color: var(--ink-2); border: 1px solid var(--rule); border-radius: 99px; padding: 2px 9px; background: var(--card); }
.unit-topics a:hover { border-color: var(--ink-3); color: var(--ink); }
.unit-stats { display: grid; gap: 8px; }
.unit-stats .stat { display: flex; justify-content: space-between; border-bottom: 1px dashed var(--rule); padding-bottom: 4px; font-size: .9rem; color: var(--ink-2); }
.unit-stats .stat b { font-size: 1.1rem; color: var(--ink); }
@media (max-width: 860px) {
  .unit-row { grid-template-columns: 1fr; gap: 10px; }
  .unit-num { font-size: 2.4rem; }
}

/* ---------- Section blocks on home ---------- */
.home-section { padding: 48px 0 8px; }
.how-grid { display: grid; grid-template-columns: repeat(4, minmax(0,1fr)); gap: 20px; margin-top: 18px; }
.how-grid div { border-left: 3px solid var(--amber); padding: 4px 0 4px 14px; }
.how-grid h4 { margin-bottom: 4px; }
.how-grid p { font-size: .93rem; color: var(--ink-2); margin: 0; }
@media (max-width: 860px) { .how-grid { grid-template-columns: 1fr 1fr; } }
@media (max-width: 520px) { .how-grid { grid-template-columns: 1fr; } }

/* ---------- Unit landing topic list ---------- */
.topic-list { list-style: none; padding: 0; margin: 0; counter-reset: t; }
.topic-item { display: grid; grid-template-columns: 54px minmax(0,1fr) auto; gap: 16px; padding: 18px 0; border-bottom: 1px solid var(--rule); align-items: start; }
.topic-item .n { font-weight: 800; font-size: 1.5rem; font-stretch: 120%; color: var(--ink-3); }
.topic-item h3 { margin-bottom: 4px; }
.topic-item h3 a { color: var(--ink); text-decoration: none; }
.topic-item h3 a:hover { text-decoration: underline; }
.topic-item p { margin: 0 0 6px; color: var(--ink-2); font-size: .95rem; }
.topic-item .sims { display: flex; gap: 6px; flex-wrap: wrap; }
@media (max-width: 640px) { .topic-item { grid-template-columns: 36px minmax(0,1fr); } .topic-item .go { grid-column: 2; } }

/* ---------- Catalog grid (sims / experiments) ---------- */
.filters { display: flex; gap: 8px; flex-wrap: wrap; margin: 0 0 18px; }
.filters button, .filters input { font: inherit; font-size: .88rem; padding: 6px 12px; border-radius: 99px; border: 1px solid var(--rule); background: var(--card); color: var(--ink); cursor: pointer; }
.filters input { border-radius: var(--radius-m); min-width: 220px; cursor: text; }
.filters button[aria-pressed="true"] { background: var(--navy); color: #fff; border-color: var(--navy); }
.catalog { display: grid; grid-template-columns: repeat(auto-fill, minmax(270px, 1fr)); gap: 14px; }
.cat-item { background: var(--card); border: 1px solid var(--rule); border-radius: var(--radius-m); padding: 14px 16px; display: flex; flex-direction: column; gap: 6px; }
.cat-item h4 { margin: 0; }
.cat-item h4 a { color: var(--ink); text-decoration: none; }
.cat-item h4 a:hover { text-decoration: underline; }
.cat-item p { margin: 0; color: var(--ink-2); font-size: .9rem; flex: 1; }
.cat-item .meta { display: flex; gap: 6px; flex-wrap: wrap; font-size: .8rem; color: var(--ink-3); }
.unit-group-h { margin: 30px 0 12px; padding-top: 10px; border-top: 2px solid var(--ink); }

.inst-line a, .site-foot a.li-badge, .about-inst a { color: inherit; text-decoration: underline; text-underline-offset: 2px; }
a.li-badge { display: inline-block; text-decoration: none !important; font: 700 .72rem/1 system-ui, sans-serif; background: #0a66c2; color: #fff !important; border-radius: 3px; padding: 2px 4px; margin-left: 4px; vertical-align: 1px; }
.about-inst { margin: -6px 0 18px; }

/* ---------- instructor card ---------- */
.inst-card { display: flex; gap: 22px; align-items: center; background: var(--card); border: 1px solid var(--rule); border-radius: var(--radius-l); padding: 20px 22px; max-width: 640px; }
.inst-card img { width: 120px; height: 120px; border-radius: 50%; object-fit: cover; flex: none; border: 3px solid var(--paper-2); }
.inst-card h3 { margin: 2px 0 2px; font-size: 1.25rem; }
.inst-card h3 a { color: inherit; }
.inst-card p { margin: 4px 0; }
.inst-card .eyebrow { font-size: .74rem; letter-spacing: .08em; text-transform: uppercase; color: var(--ink-3); font-weight: 650; }
.inst-card a.mail { color: var(--ink-2); }
.btn.sm { padding: 6px 12px; font-size: .84rem; }
@media (max-width: 520px) { .inst-card { flex-direction: column; text-align: center; } }

/* ---------- lecture slides cards (home) ---------- */
.slides-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 16px; margin-top: 14px; }
.slide-card { display: flex; flex-direction: column; background: var(--card); border: 1px solid var(--rule); border-radius: var(--radius-m); overflow: hidden; text-decoration: none; color: var(--ink); transition: transform .15s, border-color .15s; }
.slide-card:hover { transform: translateY(-2px); border-color: var(--ink-3); }
.slide-card img { width: 100%; height: auto; aspect-ratio: 16/9; display: block; border-bottom: 1px solid var(--rule); background: #fff; }
.slide-card span { padding: 10px 12px 12px; font-size: .9rem; line-height: 1.35; }
.slide-card small { display: block; color: var(--ink-3); margin-top: 4px; }

/* ---------- flipbook ---------- */
.study-note { display: inline-block; background: #fff4d6; color: #5e4300; border: 1px solid #e9c46a; border-radius: var(--radius-m); padding: 8px 12px; font-size: .92rem; }
.fb-tabs { display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px; margin: 18px 0 14px; }
.fb-tabs button { text-align: left; font: inherit; background: var(--card); color: var(--ink); border: 1px solid var(--rule); border-radius: var(--radius-m); padding: 9px 12px; cursor: pointer; line-height: 1.25; }
.fb-tabs button span { display: block; font-size: .8rem; color: var(--ink-3); }
.fb-tabs button[aria-selected="true"] { border-color: var(--amber); box-shadow: inset 0 -3px 0 var(--amber); }
@media (max-width: 760px) { .fb-tabs { grid-template-columns: repeat(2, 1fr); } .fb-tabs button span { display: none; } }
.fb { background: var(--navy); border-radius: var(--radius-l); padding: 14px; outline: none; }
.fb:focus-visible { box-shadow: 0 0 0 3px var(--signal); }
.fb-stage { perspective: 2400px; overflow: hidden; border-radius: var(--radius-m); }
.fb-stage.zoomed { overflow: auto; max-height: 78vh; cursor: grab; }
.fb-book { position: relative; width: 100%; margin: 0 auto; aspect-ratio: 16 / 9; background: #fff; box-shadow: 0 10px 30px rgba(0,0,0,.45); transform-style: preserve-3d; user-select: none; -webkit-user-select: none; }
.fb-under { position: absolute; inset: 0; width: 100%; height: 100%; display: block; }
.fb-leaf { position: absolute; inset: 0; transform-origin: left center; transform-style: preserve-3d; display: none; z-index: 2; }
.fb-face { position: absolute; inset: 0; backface-visibility: hidden; -webkit-backface-visibility: hidden; }
.fb-front img { width: 100%; height: 100%; display: block; }
.fb-front::after { content: ""; position: absolute; inset: 0; background: linear-gradient(90deg, rgba(0,0,0,0) 70%, rgba(0,0,0,.12)); }
.fb-back { transform: rotateY(180deg); background: linear-gradient(90deg, #e8ebf1, #fbfbfd 40%, #eef1f6); box-shadow: inset 0 0 40px rgba(0,0,0,.18); }
.fb-shade { position: absolute; inset: 0; background: linear-gradient(90deg, rgba(0,0,0,.5), rgba(0,0,0,0) 60%); opacity: 0; pointer-events: none; z-index: 1; }
.fb-hot { position: absolute; top: 0; bottom: 0; width: 22%; border: 0; background: transparent; cursor: pointer; z-index: 3; }
.fb-hot.prev { left: 0; cursor: w-resize; } .fb-hot.next { right: 0; cursor: e-resize; }
.fb-hot:hover { background: linear-gradient(90deg, rgba(76,194,255,.0), rgba(76,194,255,.08)); }
.fb-hot.prev:hover { background: linear-gradient(270deg, rgba(76,194,255,.0), rgba(76,194,255,.08)); }
.fb-stage.zoomed .fb-hot { display: none; }
.fb-bar { display: flex; flex-wrap: wrap; align-items: center; gap: 10px 14px; margin-top: 12px; color: var(--panel-text); }
.fb-bar .grp { display: flex; align-items: center; gap: 4px; }
.fb-bar button { font: inherit; font-size: .88rem; min-width: 36px; height: 34px; padding: 0 10px; border-radius: var(--radius-s); border: 1px solid var(--navy-line); background: var(--navy-2); color: var(--panel-text); cursor: pointer; }
.fb-bar button:hover:not(:disabled) { border-color: var(--amber); }
.fb-bar button:disabled { opacity: .4; cursor: default; }
.fb-bar button[aria-pressed="true"] { border-color: var(--amber); color: var(--amber); }
.fb-bar .pg { display: flex; align-items: center; gap: 6px; margin: 0 6px; font-size: .9rem; }
.fb-bar .pg input { width: 64px; height: 34px; border-radius: var(--radius-s); border: 1px solid var(--navy-line); background: #0a1528; color: #fff; text-align: center; font: inherit; }
.fb-bar .zv { min-width: 46px; text-align: center; font-size: .85rem; color: var(--panel-dim); }
.fb-range { flex: 1 1 200px; accent-color: var(--amber); }
.sr { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); }
.fb-thumbs { display: grid; grid-template-columns: repeat(auto-fill, minmax(130px, 1fr)); gap: 8px; margin-top: 12px; max-height: 300px; overflow: auto; padding: 4px; }
.fb-thumbs button { position: relative; padding: 0; border: 2px solid transparent; border-radius: var(--radius-s); background: #fff; cursor: pointer; }
.fb-thumbs button.on { border-color: var(--amber); }
.fb-thumbs img { width: 100%; height: auto; aspect-ratio: 16/9; display: block; }
.fb-thumbs span { position: absolute; right: 4px; bottom: 4px; font-size: .7rem; background: rgba(14,29,56,.85); color: #fff; padding: 1px 5px; border-radius: 3px; }
.fb:fullscreen { display: flex; flex-direction: column; justify-content: center; border-radius: 0; padding: 12px 20px; }
.fb:fullscreen .fb-stage:not(.zoomed) .fb-book { width: min(100%, calc((100vh - 90px) * 16 / 9)) !important; }
.fb:fullscreen .fb-stage.zoomed { max-height: calc(100vh - 80px); }
@media (prefers-reduced-motion: reduce) { .fb-leaf { display: none !important; } }
.fb-tabs { scroll-margin-top: 76px; }
.fb-stage:not(.zoomed) .fb-book { max-width: calc((100vh - 190px) * 16 / 9); min-width: 280px; }
.fb:fullscreen .fb-stage:not(.zoomed) .fb-book { max-width: none; }
.inst-card { margin-bottom: 24px; } .home-section .inst-card { margin-bottom: 0; }