:root {
  --bg: #05070b;
  --bg2: #0b1018;
  --ink: #f4f6fa;
  --muted: #9aa6b8;
  --dim: #5d6879;
  --line: rgba(255, 255, 255, 0.09);
  --card: rgba(11, 15, 23, 0.66);
  --accent: #7fd8ff;
  --radius: 22px;
  --sans: 'Inter', -apple-system, BlinkMacSystemFont, 'SF Pro Display', 'Segoe UI', Roboto, sans-serif;
  --serif: 'Newsreader', Georgia, serif;
  color-scheme: dark;
}
* { box-sizing: border-box; }
[hidden] { display: none !important; }
html { scroll-behavior: auto; -webkit-text-size-adjust: 100%; }
body {
  margin: 0; background: var(--bg); color: var(--ink); font-family: var(--sans);
  font-size: 17px; line-height: 1.55; -webkit-font-smoothing: antialiased; overflow-x: hidden;
  background-image: radial-gradient(120% 80% at 70% 10%, color-mix(in srgb, var(--accent) 9%, transparent), transparent 60%),
    radial-gradient(90% 70% at 10% 100%, rgba(80, 60, 160, 0.10), transparent 60%);
  background-attachment: fixed;
  transition: background-color .6s;
}
a { color: var(--accent); }
em { font-family: var(--serif); font-style: italic; }
button { font: inherit; color: inherit; }

#stage { position: fixed; inset: 0; width: 100%; height: 100%; z-index: 0; display: block; outline: none; touch-action: pan-y; }
#labels { position: fixed; inset: 0; z-index: 2; pointer-events: none; overflow: hidden; }
#page { position: relative; z-index: 3; pointer-events: none; }
#page > * { pointer-events: none; }
#page .card, #page .block, #page .block * { pointer-events: auto; }

/* ---------------------------------------------------------- top bar */
.topbar {
  position: fixed; top: 0; left: 0; right: 0; z-index: 20; height: 58px; display: flex; align-items: center;
  gap: 24px; padding: 0 24px; transition: background .4s, backdrop-filter .4s;
}
body.scrolled .topbar { background: rgba(5, 7, 11, 0.62); backdrop-filter: saturate(160%) blur(18px); -webkit-backdrop-filter: saturate(160%) blur(18px); border-bottom: 1px solid var(--line); }
.brand { display: flex; align-items: center; gap: 10px; color: var(--ink); text-decoration: none; font-weight: 700; letter-spacing: -0.01em; }
.brand em { color: var(--accent); font-weight: 500; }
.byline { font-family: 'Dancing Script', 'Segoe Script', cursive; font-weight: 700; letter-spacing: 0; white-space: nowrap;
  background: linear-gradient(100deg, #ffd166, #ff9fb2 60%, #b69cff); -webkit-background-clip: text; background-clip: text; color: transparent; }
.brand .byline { font-size: 1.25em; margin-left: 4px; }
.brand-dot { width: 12px; height: 12px; border-radius: 50%; background: var(--accent); box-shadow: 0 0 18px var(--accent); transition: background .6s, box-shadow .6s; }
.links { display: flex; gap: 22px; margin-left: auto; }
.links a { color: var(--muted); text-decoration: none; font-size: 14px; font-weight: 500; transition: color .2s; }
.links a:hover { color: var(--ink); }
.menu-btn { display: none; margin-left: auto; width: 40px; height: 40px; border: 0; background: transparent; position: relative; cursor: pointer; }
.menu-btn span { position: absolute; left: 10px; right: 10px; height: 2px; background: var(--ink); border-radius: 2px; transition: transform .3s; }
.menu-btn span:first-child { top: 15px; } .menu-btn span:last-child { top: 23px; }
body.menu-open .menu-btn span:first-child { transform: translateY(4px) rotate(45deg); }
body.menu-open .menu-btn span:last-child { transform: translateY(-4px) rotate(-45deg); }
#progress { position: absolute; left: 0; right: 0; bottom: -1px; height: 2px; }
#progress i { display: block; height: 100%; background: linear-gradient(90deg, var(--accent), #fff); transform-origin: left; transform: scaleX(0); }

/* ---------------------------------------------------------- index (toc) */
#toc {
  position: fixed; right: 14px; top: 50%; transform: translateY(-50%); z-index: 15; display: flex; flex-direction: column;
  gap: 1px; max-height: 86vh; overflow-y: auto; scrollbar-width: none; padding: 8px 6px;
}
#toc::-webkit-scrollbar { display: none; }
#toc .toc-ch { display: none; margin: 10px 0 4px; font-size: 11px; text-transform: uppercase; letter-spacing: .12em; color: var(--dim); }
#toc a { display: flex; align-items: center; justify-content: flex-end; gap: 10px; height: 18px; text-decoration: none; color: var(--muted); font-size: 12.5px; }
#toc a span { opacity: 0; transform: translateX(6px); transition: .25s; white-space: nowrap; }
#toc a i { width: 6px; height: 6px; border-radius: 50%; background: rgba(255, 255, 255, .28); flex: none; transition: .3s; }
#toc a.on i { background: var(--accent); box-shadow: 0 0 10px var(--accent); transform: scale(1.6); }
#toc a.on span { opacity: 1; transform: none; color: var(--ink); }
#toc:hover { background: rgba(5, 7, 11, .78); backdrop-filter: blur(14px); border-radius: 16px; }
#toc:hover a span { opacity: 1; transform: none; }
#toc:hover .toc-ch { display: block; text-align: right; }

/* ---------------------------------------------------------- generic */
.kicker { margin: 0 0 10px; font-size: 13px; font-weight: 600; letter-spacing: .14em; text-transform: uppercase; color: var(--accent); transition: color .6s; }
.btn { display: inline-flex; align-items: center; gap: 8px; padding: 12px 20px; border-radius: 999px; border: 1px solid var(--line); background: rgba(255, 255, 255, .06); color: var(--ink); text-decoration: none; font-weight: 600; font-size: 15px; cursor: pointer; transition: transform .2s, background .2s, border-color .2s; }
.btn:hover { transform: translateY(-1px); background: rgba(255, 255, 255, .1); }
.btn.primary { background: var(--accent); color: #04121c; border-color: transparent; }
.btn.primary:hover { filter: brightness(1.08); }
.fine { font-size: 13px; color: var(--dim); }

/* ---------------------------------------------------------- hero */
.hero { min-height: 100svh; display: flex; align-items: center; padding: 90px 6vw 60px; }
.hero-inner { max-width: 620px; }
.hero-title { font-size: clamp(64px, 10.5vw, 168px); line-height: .88; letter-spacing: -0.055em; margin: 6px 0 26px; font-weight: 800; }
.hero-title span { background: linear-gradient(100deg, #fff 10%, var(--accent) 55%, #b69cff 95%); -webkit-background-clip: text; background-clip: text; color: transparent; }
.hero-sub { font-size: clamp(18px, 1.6vw, 22px); color: var(--muted); max-width: 520px; margin: 0 0 30px; }
.hero-cta { display: flex; gap: 12px; flex-wrap: wrap; }
.hero-hint { margin-top: 56px; display: flex; align-items: center; gap: 12px; color: var(--dim); font-size: 13px; letter-spacing: .1em; text-transform: uppercase; }
.mouse { width: 22px; height: 34px; border: 2px solid var(--dim); border-radius: 12px; position: relative; }
.mouse::after { content: ''; position: absolute; left: 50%; top: 6px; width: 3px; height: 7px; margin-left: -1.5px; background: var(--dim); border-radius: 2px; animation: wheel 1.8s infinite; }
@keyframes wheel { 0% { opacity: 1; transform: none; } 80% { opacity: 0; transform: translateY(10px); } 100% { opacity: 0; } }

/* ---------------------------------------------------------- divider */
.divider { min-height: 100svh; display: grid; place-items: center; text-align: center; padding: 120px 8vw;
  background: radial-gradient(60% 50% at 50% 50%, color-mix(in srgb, var(--accent) 12%, transparent), transparent 70%); }
.divider-inner { max-width: 980px; }
.divider h2 { font-size: clamp(56px, 11vw, 176px); letter-spacing: -0.055em; line-height: .9; margin: 0 0 28px; font-weight: 800;
  background: linear-gradient(180deg, #fff 30%, color-mix(in srgb, var(--accent) 70%, #fff)); -webkit-background-clip: text; background-clip: text; color: transparent; }
.divider p:not(.kicker) { font-size: clamp(19px, 2vw, 26px); color: var(--muted); max-width: 760px; margin: 0 auto; }

/* ---------------------------------------------------------- stories */
.story { position: relative; padding: 4vh 0 10vh; }
.step { min-height: 82vh; display: flex; align-items: center; padding: 0 0 0 5.5vw; width: min(42vw, 560px); }
.step.intro { min-height: 100vh; }
.card {
  position: relative; width: 100%; max-width: 460px; padding: 26px 28px; border-radius: var(--radius);
  background: var(--card); border: 1px solid var(--line); backdrop-filter: blur(22px) saturate(150%); -webkit-backdrop-filter: blur(22px) saturate(150%);
  box-shadow: 0 30px 80px -30px rgba(0, 0, 0, .6);
  opacity: .28; transform: translateY(24px) scale(.98); transition: opacity .6s, transform .7s cubic-bezier(.2, .8, .2, 1), border-color .6s;
}
.step.active .card { opacity: 1; transform: none; border-color: color-mix(in srgb, var(--accent) 35%, transparent); }
.card h3 { font-size: 26px; line-height: 1.15; letter-spacing: -0.02em; margin: 6px 0 10px; }
.card p { margin: 0 0 10px; color: #c8d0dc; }
.card p:last-child { margin-bottom: 0; }
.card .num { font-size: 13px; font-weight: 700; color: var(--accent); letter-spacing: .08em; }
.card .num i { font-style: normal; color: var(--dim); }
.card .tag { display: inline-block; font-size: 12.5px; font-weight: 600; color: var(--accent); background: color-mix(in srgb, var(--accent) 12%, transparent); padding: 4px 10px; border-radius: 99px; margin-bottom: 12px; }
.intro-card { max-width: 520px; padding: 34px 34px 30px; }
.intro-card .title { font-size: clamp(46px, 5.6vw, 84px); line-height: .95; letter-spacing: -0.05em; margin: 0 0 14px; font-weight: 800; }
.intro-card .title small { font-size: .38em; letter-spacing: -0.01em; color: var(--muted); font-weight: 600; }
.intro-card .meaning { font-family: var(--serif); font-style: italic; font-size: 20px; color: #dfe6f0; }
.intro-card .common { color: var(--muted); font-size: 15px; }
.intro-card .common em { color: var(--ink); }
.intro-card .stat { font-size: 15px; font-weight: 700; color: var(--accent); }
.intro-card .lead { font-size: 18px; }
.glance { display: grid; grid-template-columns: repeat(auto-fill, minmax(140px, 1fr)); gap: 8px; margin: 18px 0 14px; }
.glance div { background: rgba(255, 255, 255, .04); border: 1px solid var(--line); border-radius: 14px; padding: 9px 12px; }
.glance dt { font-size: 11px; text-transform: uppercase; letter-spacing: .1em; color: var(--dim); }
.glance dd { margin: 2px 0 0; font-weight: 600; font-size: 14.5px; }
.scroll-hint { font-size: 13px; color: var(--dim) !important; letter-spacing: .04em; }
.chips { list-style: none; padding: 0; margin: 10px 0 18px; display: flex; flex-wrap: wrap; gap: 8px; }
.chips li { background: rgba(255, 255, 255, .05); border: 1px solid var(--line); border-radius: 12px; padding: 7px 12px; display: flex; flex-direction: column; }
.chips em { font-size: 17px; color: var(--ink); }
.chips span { font-size: 12px; color: var(--muted); }
.ex-actions { display: flex; gap: 10px; flex-wrap: wrap; margin-bottom: 8px; }

/* ---------------------------------------------------------- labels */
.lbl { position: absolute; inset: 0; opacity: 0; transition: opacity .45s; }
.lbl.on { opacity: 1; }
.lbl-dot { position: absolute; left: -5px; top: -5px; width: 10px; height: 10px; border-radius: 50%; background: var(--accent); box-shadow: 0 0 0 3px rgba(0, 0, 0, .45), 0 0 16px var(--accent); }
.lbl-line { position: absolute; left: 0; top: 0; height: 1.5px; background: linear-gradient(90deg, var(--accent), rgba(255, 255, 255, .7)); transform-origin: 0 50%; }
.lbl-txt { position: absolute; left: 0; top: 0; white-space: nowrap; font-size: 13.5px; font-weight: 600; padding: 6px 11px; border-radius: 10px;
  background: rgba(6, 9, 14, .82); border: 1px solid color-mix(in srgb, var(--accent) 45%, transparent); color: #fff; backdrop-filter: blur(8px); }
.lbl.sec .lbl-dot { width: 7px; height: 7px; left: -3.5px; top: -3.5px; background: #fff; box-shadow: 0 0 0 2px rgba(0, 0, 0, .5); }
.lbl.sec .lbl-txt { font-size: 12px; font-weight: 500; padding: 4px 9px; border-color: rgba(255, 255, 255, .25); }
.lbl.sec .lbl-line { background: rgba(255, 255, 255, .6); height: 1px; }
.lbl.sym .lbl-dot { display: none; }
.lbl.sym .lbl-line { display: none; }
.lbl.sym .lbl-txt { font-family: var(--serif); font-style: italic; font-weight: 500; font-size: 15px; border-color: rgba(125, 249, 255, .45); }

/* ---------------------------------------------------------- tree / table / quiz blocks */
.treeblock, .tableblock, .quizblock {
  position: relative; padding: 120px 6vw 110px; background: rgba(5, 7, 11, .86); backdrop-filter: blur(16px); -webkit-backdrop-filter: blur(16px);
  border-top: 1px solid var(--line); border-bottom: 1px solid var(--line);
}
.tree-head { max-width: 860px; margin: 0 auto 36px; text-align: center; }
.tree-head h2 { font-size: clamp(36px, 5vw, 66px); letter-spacing: -0.045em; line-height: 1; margin: 0 0 14px; }
.tree-head p:not(.kicker) { color: var(--muted); font-size: 18px; margin: 0; }
.tree-scroll { overflow-x: auto; max-width: 1100px; margin: 0 auto; -webkit-overflow-scrolling: touch; }
.tree-svg { width: 100%; min-width: 760px; height: auto; display: block; font-family: var(--sans); }
.tree-svg .col { fill: var(--dim); font-size: 12px; letter-spacing: .12em; text-transform: uppercase; font-weight: 600; }
.tree-svg .edge { fill: none; stroke: rgba(255, 255, 255, .18); stroke-width: 1.6; transition: stroke .3s, stroke-width .3s; }
.tree-svg .edge.hot { stroke: var(--accent); stroke-width: 2.6; }
.tree-svg .node rect { fill: #111826; stroke: rgba(255, 255, 255, .14); transition: .3s; }
.tree-svg .node text { fill: #dbe3ee; font-size: 13px; font-weight: 600; }
.tree-svg .node .sub { fill: var(--dim); font-size: 11px; font-weight: 500; }
.tree-svg .node.leaf { cursor: pointer; }
.tree-svg .node.leaf rect { fill: color-mix(in srgb, var(--accent) 16%, #0d131d); stroke: color-mix(in srgb, var(--accent) 50%, transparent); }
.tree-svg .node.hot rect { fill: color-mix(in srgb, var(--accent) 30%, #0d131d); stroke: var(--accent); }
.tree-svg .node.leaf:focus { outline: none; }
.tree-svg .node.leaf:focus rect { stroke-width: 2.5; }
.treeblock .fine { text-align: center; }

.table-scroll { overflow-x: auto; max-width: 1240px; margin: 0 auto; border-radius: 18px; border: 1px solid var(--line); }
table.features { border-collapse: collapse; width: 100%; min-width: 980px; font-size: 14px; }
.features th, .features td { padding: 12px 14px; text-align: left; border-bottom: 1px solid var(--line); vertical-align: middle; }
.features thead th { font-size: 11.5px; text-transform: uppercase; letter-spacing: .08em; color: var(--muted); background: #0b111a; position: sticky; top: 0; }
.features tbody th { font-weight: 700; white-space: nowrap; }
.features tbody tr { cursor: pointer; transition: background .2s; }
.features tbody tr:hover { background: rgba(255, 255, 255, .04); }
.features .col-hot { background: color-mix(in srgb, var(--accent) 10%, transparent); }
.pill { display: inline-block; padding: 3px 9px; border-radius: 99px; font-size: 12.5px; font-weight: 600; background: rgba(255, 255, 255, .07); white-space: nowrap; }
.pill.no { color: #7d8797; }
.pill.yes { background: rgba(84, 214, 140, .14); color: #7ff0b0; }
.pill.mid { background: rgba(255, 193, 92, .14); color: #ffd27f; }

.quiz-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(290px, 1fr)); gap: 16px; max-width: 1180px; margin: 0 auto 22px; }
.qcard, .match { background: #0d131d; border: 1px solid var(--line); border-radius: 20px; padding: 22px; }
.qn { font-size: 12px; font-weight: 700; letter-spacing: .1em; color: var(--accent); margin: 0 0 6px; }
.qq { font-weight: 600; margin: 0 0 14px; }
.opts { display: grid; gap: 8px; }
.opts button { text-align: left; padding: 10px 14px; border-radius: 12px; border: 1px solid var(--line); background: rgba(255, 255, 255, .03); cursor: pointer; transition: .2s; }
.opts button:hover { border-color: color-mix(in srgb, var(--accent) 50%, transparent); }
.opts button.right { background: rgba(84, 214, 140, .16); border-color: #54d68c; }
.opts button.wrong { background: rgba(255, 99, 99, .14); border-color: #ff6363; }
.qfb { margin: 12px 0 0; font-size: 14px; color: var(--muted); min-height: 1em; }
.match { max-width: 1180px; margin: 0 auto; }
.match-rows { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 10px 18px; margin: 10px 0 18px; }
.match label { display: flex; align-items: center; justify-content: space-between; gap: 10px; padding: 8px 10px 8px 14px; border-radius: 12px; border: 1px solid var(--line); }
.match label.right { border-color: #54d68c; } .match label.wrong { border-color: #ff6363; }
.match select { background: #121a26; color: var(--ink); border: 1px solid var(--line); border-radius: 8px; padding: 6px 8px; font: inherit; font-size: 14px; max-width: 60%; }

/* ---------------------------------------------------------- footer */
.foot { padding: 120px 6vw 80px; background: #04060a; border-top: 1px solid var(--line); }
.foot-inner { max-width: 980px; margin: 0 auto; }
.foot h2 { font-size: clamp(36px, 5vw, 60px); letter-spacing: -0.045em; margin: 0 0 18px; }
.foot h2 span { color: var(--accent); }
.foot h2 .byline { color: transparent; display: inline-block; font-size: .78em; margin-left: .2em; padding-right: .1em; }
.more-btn {
  position: relative; display: inline-flex; align-items: center; gap: 12px; margin: 4px 0 12px; padding: 16px 26px 16px 28px;
  border-radius: 999px; text-decoration: none; color: #04121c; font-weight: 800; font-size: 15px; letter-spacing: .08em;
  background: linear-gradient(100deg, var(--accent), #b69cff 55%, #ff9fb2);
  background-size: 200% 100%; background-position: 0 0;
  box-shadow: 0 10px 34px -8px color-mix(in srgb, var(--accent) 70%, transparent), inset 0 1px 0 rgba(255, 255, 255, .45);
  transition: transform .25s cubic-bezier(.2, .8, .2, 1), box-shadow .25s, background-position .6s;
}
.more-btn svg { transition: transform .25s; }
.more-btn:hover { transform: translateY(-2px); background-position: 100% 0; box-shadow: 0 16px 44px -8px color-mix(in srgb, #b69cff 75%, transparent), inset 0 1px 0 rgba(255, 255, 255, .5); }
.more-btn:hover svg { transform: translateX(4px); }
.more-btn:focus-visible { outline: 2px solid #fff; outline-offset: 3px; }
.support {
  display: grid; grid-template-columns: 1fr auto; gap: 28px; align-items: center; margin: 34px 0 6px; padding: 28px;
  border-radius: 24px; border: 1px solid color-mix(in srgb, #ffd166 35%, transparent);
  background: radial-gradient(120% 140% at 0% 0%, rgba(255, 209, 102, .10), transparent 60%), rgba(255, 255, 255, .02);
}
.support .kicker { color: #ffd166; }
.support h3 { margin: 0 0 8px; font-size: clamp(22px, 2.4vw, 30px); letter-spacing: -0.02em; }
.support p { margin: 0 0 14px; }
.support-actions { display: flex; flex-wrap: wrap; gap: 10px; margin: 6px 0 12px; }
.support .upi-pay { background: #ffd166; color: #1b1300; }
.support .coffee { background: rgba(255, 255, 255, .08); }
.copy-upi { margin-left: 6px; padding: 2px 10px; border-radius: 99px; border: 1px solid var(--line); background: rgba(255, 255, 255, .06); font-size: 12px; cursor: pointer; }
.institutions { font-size: 15px; padding-top: 12px; border-top: 1px solid var(--line); margin-top: 6px !important; }
.upi-qr { text-align: center; }
.upi-qr-code { width: 180px; height: 180px; padding: 10px; border-radius: 16px; background: #fff; margin: 0 auto 8px; }
.upi-qr-code svg { width: 100%; height: 100%; display: block; }
.upi-qr p { font-size: 12.5px; color: var(--dim); margin: 0; max-width: 180px; }
.upi-pay { display: none !important; }
@media (pointer: coarse) { .upi-pay { display: inline-flex !important; } }
@media (max-width: 899px) {
  .support { grid-template-columns: 1fr; padding: 22px 18px; }
  .upi-qr { order: -1; }
}
@media (max-width: 899px) { .more-btn { font-size: 13px; padding: 14px 20px; letter-spacing: .05em; } }
.foot p { color: var(--muted); }
.foot .license { margin-top: 28px; padding-top: 22px; border-top: 1px solid var(--line); font-size: 14px; }
.license a { color: var(--ink); }
.license img { height: 18px; margin-left: 4px; vertical-align: text-bottom; filter: invert(1); opacity: .85; }
.ar-help { display: grid; grid-template-columns: repeat(auto-fit, minmax(230px, 1fr)); gap: 14px; margin: 30px 0; }
.ar-help div { border: 1px solid var(--line); border-radius: 18px; padding: 18px; background: rgba(255, 255, 255, .02); }
.ar-help h4 { margin: 0 0 6px; }
.ar-help p { margin: 0; font-size: 15px; }

/* ---------------------------------------------------------- toolbar & panels */
.toolbar {
  position: fixed; z-index: 12; left: 66.5%; transform: translate(-50%, 20px); bottom: 26px; display: flex; align-items: center; gap: 6px;
  padding: 6px 6px 6px 16px; border-radius: 999px; background: rgba(9, 13, 20, .72); border: 1px solid var(--line);
  backdrop-filter: blur(18px) saturate(160%); -webkit-backdrop-filter: blur(18px) saturate(160%);
  opacity: 0; pointer-events: none; transition: opacity .4s, transform .5s cubic-bezier(.2, .8, .2, 1);
}
body.has-model .toolbar { opacity: 1; pointer-events: auto; transform: translate(-50%, 0); }
.tb-name { font-family: var(--serif); font-style: italic; font-size: 16px; color: #e3e9f2; margin-right: 6px; white-space: nowrap; max-width: 22vw; overflow: hidden; text-overflow: ellipsis; }
.tb-btn { white-space: nowrap; display: inline-flex; align-items: center; gap: 7px; border: 0; background: rgba(255, 255, 255, .07); padding: 9px 14px; border-radius: 999px; cursor: pointer; font-size: 14px; font-weight: 600; transition: background .2s; }
.tb-btn:hover { background: rgba(255, 255, 255, .14); }
.tb-btn.ar { background: var(--accent); color: #04121c; }
.tb-btn[hidden] { display: none; }
.tb-load { width: 16px; height: 16px; border-radius: 50%; border: 2px solid rgba(255, 255, 255, .2); border-top-color: var(--accent); display: none; animation: spin .8s linear infinite; }
body.loading .tb-load { display: block; }
@keyframes spin { to { transform: rotate(360deg); } }

.parts-panel {
  position: fixed; z-index: 13; right: 22px; bottom: 90px; width: 300px; max-height: 60vh; overflow-y: auto; padding: 16px;
  border-radius: 20px; background: rgba(9, 13, 20, .9); border: 1px solid var(--line); backdrop-filter: blur(18px);
  opacity: 0; transform: translateY(12px); pointer-events: none; transition: .35s;
}
.parts-panel.open { opacity: 1; transform: none; pointer-events: auto; }
.pp-h { margin: 0 0 8px; font-size: 12px; text-transform: uppercase; letter-spacing: .1em; color: var(--dim); }
.pp-model { margin: 10px 0 6px; font-family: var(--serif); font-style: italic; color: var(--muted); }
.pp-group { display: flex; flex-wrap: wrap; gap: 6px; }
.pp-group .pp-model { flex-basis: 100%; }
.parts-panel button { border: 1px solid var(--line); background: rgba(255, 255, 255, .04); padding: 6px 11px; border-radius: 99px; font-size: 13px; cursor: pointer; }
.parts-panel button.on, .parts-panel button:hover { border-color: var(--accent); color: var(--accent); }
.pick-toast { position: fixed; z-index: 14; left: 50%; top: 76px; transform: translate(-50%, -10px); padding: 9px 16px; border-radius: 99px; background: rgba(9, 13, 20, .9); border: 1px solid var(--accent); font-weight: 600; opacity: 0; transition: .3s; pointer-events: none; }
.pick-toast.on { opacity: 1; transform: translate(-50%, 0); }

.explore-bar { position: fixed; z-index: 16; top: 70px; left: 50%; transform: translate(-50%, -20px); display: flex; align-items: center; gap: 14px; padding: 8px 8px 8px 18px; border-radius: 999px; background: rgba(9, 13, 20, .8); border: 1px solid var(--line); backdrop-filter: blur(16px); opacity: 0; pointer-events: none; transition: .35s; }
.explore-bar p { margin: 0; font-size: 14px; color: var(--muted); }
body.exploring .explore-bar { opacity: 1; transform: translate(-50%, 0); pointer-events: auto; }
body.exploring #page, body.exploring #toc { opacity: 0; pointer-events: none !important; }
body.exploring #page * { pointer-events: none !important; }
body.exploring #stage { z-index: 10; touch-action: none; }
body.exploring .toolbar { left: 50%; }
#page, #toc { transition: opacity .4s; }

.modal { position: fixed; inset: 0; z-index: 30; display: grid; place-items: center; background: rgba(0, 0, 0, .6); backdrop-filter: blur(8px); opacity: 0; pointer-events: none; transition: .3s; padding: 16px; }
.modal.open { opacity: 1; pointer-events: auto; }
.modal-card { position: relative; width: min(420px, 100%); background: #0d131d; border: 1px solid var(--line); border-radius: 24px; padding: 28px; text-align: center; }
.modal-card h3 { margin: 0 0 8px; font-family: var(--serif); font-style: italic; font-weight: 500; font-size: 28px; }
.modal-card p { color: var(--muted); font-size: 15px; }
#qr { width: 220px; height: 220px; margin: 14px auto; background: #fff; border-radius: 16px; padding: 10px; }
#qr svg { width: 100%; height: 100%; display: block; }
#qr-url { word-break: break-all; }
.modal-x { position: absolute; right: 14px; top: 10px; border: 0; background: transparent; font-size: 28px; color: var(--muted); cursor: pointer; }
.ar-arrive { position: fixed; z-index: 25; left: 50%; bottom: 90px; transform: translateX(-50%); box-shadow: 0 10px 40px rgba(0, 0, 0, .5); }

/* ---------------------------------------------------------- mobile */
@media (max-width: 899px) {
  body { font-size: 16px; }
  .links { display: none; }
  .menu-btn { display: block; }
  .topbar { padding: 0 16px; }
  .brand { font-size: 15px; }
  .brand .byline { display: block; font-size: 1.05em; margin: -3px 0 0; line-height: 1.1; }
  #toc { display: none; }
  body.menu-open #toc {
    display: flex; inset: 58px 0 0 0; right: 0; top: 58px; transform: none; max-height: none; padding: 18px 22px 40px;
    background: rgba(5, 7, 11, .96); backdrop-filter: blur(20px);
  }
  body.menu-open #toc a { justify-content: flex-start; height: 34px; font-size: 16px; flex-direction: row-reverse; }
  body.menu-open #toc a span { opacity: 1; transform: none; color: var(--ink); }
  body.menu-open #toc .toc-ch { display: block; }
  .hero { align-items: flex-end; padding: 90px 16px 40px; min-height: 100svh; }
  .hero-inner { background: linear-gradient(transparent, rgba(5, 7, 11, .85) 30%); padding-top: 30px; }
  .hero-hint { margin-top: 26px; }
  .step { width: 100%; min-height: 100svh; align-items: flex-end; padding: 0 12px 92px; }
  .step.intro { min-height: 100svh; }
  .card { max-width: none; padding: 20px 20px 18px; border-radius: 20px; background: rgba(9, 13, 20, .8); }
  .card h3 { font-size: 22px; }
  .intro-card { padding: 24px 22px; }
  .glance { grid-template-columns: repeat(2, 1fr); }
  .toolbar { left: 50%; bottom: 14px; max-width: calc(100% - 20px); padding-left: 12px; }
  .tb-name { display: none; }
  .tb-btn { padding: 9px 12px; }
  .tb-btn span { font-size: 13px; }
  #stage { pointer-events: none; }
  body.exploring #stage { pointer-events: auto; }
  .parts-panel { left: 10px; right: 10px; width: auto; bottom: 74px; }
  .explore-bar { top: auto; bottom: 80px; flex-direction: column; border-radius: 20px; text-align: center; padding: 12px 16px; width: calc(100% - 24px); }
  .treeblock, .tableblock, .quizblock { padding: 90px 16px 80px; }
  .lbl-txt { font-size: 12px; padding: 4px 8px; }
}
@media (prefers-reduced-motion: reduce) {
  .card, .toolbar, .lbl { transition: none; }
}