:root {
    --ink: #101828;
    --ink-soft: #475467;
    --ink-faint: #98a2b3;
    --paper: #ffffff;
    --paper-warm: #faf9f7;
    --line: #eaecf0;
    --accent: #e8590c;
    --accent-bright: #ff9500;
    --accent-soft: #fff3e8;
    --navy: #0c1524;
    --radius: 14px;
    --shadow-lg: 0 24px 60px -12px rgba(16, 24, 40, .18);
    --shadow-sm: 0 2px 8px rgba(16, 24, 40, .06);
  }
  * { margin: 0; padding: 0; box-sizing: border-box; }
  html { scroll-behavior: smooth; }
  body {
    font-family: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Segoe UI", Helvetica, Arial, sans-serif;
    color: var(--ink);
    background: var(--paper);
    -webkit-font-smoothing: antialiased;
    line-height: 1.55;
  }
  .wrap { max-width: 1120px; margin: 0 auto; padding: 0 24px; }
  h1, h2, h3 { letter-spacing: -0.02em; line-height: 1.12; font-weight: 700; }
  h2 { font-size: clamp(28px, 4vw, 40px); }
  .kicker {
    display: inline-block; font-size: 13px; font-weight: 600; letter-spacing: .08em;
    text-transform: uppercase; color: var(--accent); margin-bottom: 14px;
  }
  .lede { color: var(--ink-soft); font-size: 18px; max-width: 580px; }
  section { padding: 96px 0; }
  .badge {
    display: inline-block; font-size: 12px; font-weight: 700; letter-spacing: .06em;
    text-transform: uppercase; color: var(--accent); background: var(--accent-soft);
    border-radius: 999px; padding: 4px 12px; margin-left: 10px; vertical-align: middle;
  }

  /* ---------- nav ---------- */
  nav {
    position: sticky; top: 0; z-index: 50;
    background: rgba(255,255,255,.86); backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--line);
  }
  .nav-inner { display: flex; align-items: center; justify-content: space-between; height: 64px; }
  .logo { display: flex; align-items: center; gap: 9px; font-weight: 700; font-size: 18px; color: var(--ink); text-decoration: none; }
  .logo svg { display: block; }
  .nav-links { display: flex; gap: 28px; align-items: center; }
  .nav-links a { color: var(--ink-soft); text-decoration: none; font-size: 15px; font-weight: 500; }
  .nav-links a:hover { color: var(--ink); }
  .btn {
    display: inline-block; padding: 10px 20px; border-radius: 10px; font-weight: 600;
    font-size: 15px; text-decoration: none; transition: transform .12s ease, box-shadow .12s ease;
  }
  .btn-primary { background: var(--ink); color: #fff; }
  .btn-primary:hover { transform: translateY(-1px); box-shadow: 0 8px 20px rgba(16,24,40,.2); }
  .btn-accent { background: var(--accent); color: #fff; }
  .btn-accent:hover { transform: translateY(-1px); box-shadow: 0 8px 20px rgba(232,89,12,.32); }
  .btn-ghost { color: var(--ink); border: 1px solid var(--line); background: #fff; }
  .btn-ghost:hover { border-color: var(--ink-faint); }
  .btn-lg { padding: 14px 28px; font-size: 16px; border-radius: 12px; }
  @media (max-width: 720px) { .nav-links a:not(.btn) { display: none; } }

  /* ---------- hero ---------- */
  .hero { padding: 88px 0 40px; background:
    radial-gradient(1200px 500px at 70% -10%, var(--accent-soft), transparent 65%), var(--paper); }
  .hero h1 { font-size: clamp(44px, 7vw, 76px); max-width: 800px; }
  .hero h1 em { font-style: normal; position: relative; white-space: nowrap; }
  .hero h1 em svg { position: absolute; left: -5%; top: -14%; width: 110%; height: 128%; overflow: visible; }
  .hero .lede { margin: 22px 0 32px; font-size: 19px; max-width: 620px; }
  .hero-ctas { display: flex; gap: 14px; flex-wrap: wrap; align-items: center; }
  .hero-note { font-size: 13.5px; color: var(--ink-faint); margin-top: 14px; }
  kbd {
    font-family: inherit; background: #fff; border: 1px solid var(--line); border-bottom-width: 2px;
    border-radius: 6px; padding: 1px 7px; font-size: .85em; font-weight: 600; color: var(--ink);
  }

  /* ---------- hero demo mock ---------- */
  .demo { margin: 64px auto 0; position: relative; max-width: 960px; filter: drop-shadow(0 40px 80px rgba(16,24,40,.16)); }
  .screen {
    background: linear-gradient(180deg, #f2f0ec, #e9e6e0); border-radius: 18px;
    border: 1px solid var(--line); padding: 34px 30px 42px; position: relative; overflow: hidden;
  }
  .doc {
    background: #fff; border-radius: 10px; box-shadow: var(--shadow-sm); border: 1px solid var(--line);
    max-width: 470px; padding: 26px 30px; font-size: 15px; color: var(--ink-soft);
  }
  .doc .doc-bar { display: flex; align-items: center; gap: 6px; margin-bottom: 18px; }
  .doc .dot { width: 10px; height: 10px; border-radius: 50%; background: #e5e3df; }
  .doc .doc-title { margin-left: 8px; font-size: 12.5px; color: var(--ink-faint); font-weight: 500; }
  .doc h4 { color: var(--ink); font-size: 15px; margin-bottom: 12px; }
  .mathline { font-family: "SF Mono", ui-monospace, Menlo, monospace; font-size: 15.5px; color: var(--ink); margin: 10px 0; }
  .mathline.problem { position: relative; display: inline-block; padding: 2px 6px; }
  .ring { position: absolute; inset: -10px -16px; width: calc(100% + 32px); height: calc(100% + 20px); overflow: visible; pointer-events: none; }
  .ring ellipse {
    fill: none; stroke: var(--accent-bright); stroke-width: 3; stroke-linecap: round;
    stroke-dasharray: 320; stroke-dashoffset: 320; animation: drawring 1.1s ease-out .6s forwards;
    transform: rotate(-2deg); transform-origin: center;
  }
  @keyframes drawring { to { stroke-dashoffset: 0; } }
  .pill {
    position: absolute; left: 300px; top: 148px; background: var(--accent-bright); color: #fff;
    font-size: 13px; font-weight: 600; padding: 6px 12px; border-radius: 999px;
    box-shadow: 0 6px 16px rgba(232,89,12,.35); opacity: 0; animation: pop .4s ease 1.7s forwards;
  }
  @keyframes pop { from { opacity: 0; transform: translateY(6px) scale(.92); } to { opacity: 1; transform: none; } }
  .tutor-panel {
    position: absolute; right: 26px; top: 30px; width: 340px; background: rgba(255,255,255,.97);
    border-radius: 14px; box-shadow: var(--shadow-lg); border: 1px solid var(--line);
    padding: 18px 18px 14px; opacity: 0; animation: pop .5s ease 2.1s forwards;
  }
  .tutor-panel .tp-head { display: flex; justify-content: space-between; align-items: center; margin-bottom: 10px; }
  .tutor-panel .tp-title { font-size: 12px; font-weight: 700; letter-spacing: .06em; text-transform: uppercase; color: var(--accent); }
  .tutor-panel .tp-x { color: var(--ink-faint); font-size: 13px; }
  .tutor-panel p { font-size: 14px; color: var(--ink); margin-bottom: 10px; }
  .tp-input {
    display: flex; justify-content: space-between; align-items: center; border: 1px solid var(--line);
    border-radius: 9px; padding: 8px 12px; font-size: 13px; color: var(--ink-faint); margin-top: 12px;
  }
  .tp-input span:last-child { color: var(--ink-soft); font-weight: 600; font-size: 12.5px; }
  @media (max-width: 860px) {
    .tutor-panel { position: static; width: auto; margin-top: 22px; }
    .pill { left: 46%; top: 200px; }
  }

  /* ---------- trust strip ---------- */
  .trust { padding: 28px 0 8px; }
  .trust-row { display: flex; gap: 12px 34px; flex-wrap: wrap; justify-content: center; color: var(--ink-faint); font-size: 14px; font-weight: 500; }
  .trust-row span::before { content: "•"; color: var(--accent-bright); margin-right: 9px; }

  /* ---------- why / compare ---------- */
  .why { text-align: center; }
  .why h2 { max-width: 700px; margin: 0 auto; }
  .why .lede { margin: 20px auto 0; }
  .compare { display: grid; grid-template-columns: repeat(3, 1fr); gap: 22px; margin-top: 52px; text-align: left; }
  .compare .card h3 { display: flex; align-items: center; gap: 8px; }
  .compare .dim { opacity: .72; }
  .compare .win { border-color: var(--accent-bright); box-shadow: 0 8px 30px rgba(232,89,12,.12); }
  @media (max-width: 820px) { .compare { grid-template-columns: 1fr; } }

  /* ---------- how it works ---------- */
  .steps { display: grid; grid-template-columns: repeat(3, 1fr); gap: 28px; margin-top: 52px; }
  .step { background: var(--paper-warm); border: 1px solid var(--line); border-radius: var(--radius); padding: 30px 28px; }
  .step .num {
    width: 34px; height: 34px; border-radius: 50%; background: var(--accent-soft); color: var(--accent);
    display: flex; align-items: center; justify-content: center; font-weight: 700; margin-bottom: 18px; font-size: 15px;
  }
  .step h3 { font-size: 19px; margin-bottom: 8px; }
  .step p { color: var(--ink-soft); font-size: 15px; }
  @media (max-width: 820px) { .steps { grid-template-columns: 1fr; } }

  /* ---------- features / cards ---------- */
  .features { background: var(--paper-warm); border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); }
  .grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 22px; margin-top: 52px; }
  .card { background: #fff; border: 1px solid var(--line); border-radius: var(--radius); padding: 28px 26px; }
  .card .ico {
    width: 40px; height: 40px; border-radius: 10px; background: var(--accent-soft);
    display: flex; align-items: center; justify-content: center; margin-bottom: 18px;
    color: var(--accent); font-size: 19px;
  }
  .card h3 { font-size: 17.5px; margin-bottom: 8px; }
  .card p { color: var(--ink-soft); font-size: 14.5px; }
  .card .tag { font-size: 12px; font-weight: 700; letter-spacing: .05em; text-transform: uppercase; color: var(--accent); margin-bottom: 10px; display: block; }
  .card .snippet {
    font-family: "SF Mono", ui-monospace, Menlo, monospace; font-size: 12.5px; background: var(--paper-warm);
    border: 1px solid var(--line); border-radius: 8px; padding: 12px 14px; margin: 14px 0; color: var(--ink);
    overflow-x: auto; white-space: pre;
  }
  .card .snippet .hl { background: var(--accent-soft); border-bottom: 2px solid var(--accent-bright); padding: 0 2px; }
  .card .margin-q { font-size: 13.5px; color: var(--ink); background: var(--accent-soft); border-radius: 8px; padding: 10px 13px; }
  .card .margin-q b { color: var(--accent); }
  @media (max-width: 900px) { .grid { grid-template-columns: 1fr 1fr; } }
  @media (max-width: 620px) { .grid { grid-template-columns: 1fr; } }

  /* ---------- personas ---------- */
  .persona { display: grid; grid-template-columns: 1fr 1fr; gap: 60px; align-items: center; margin-top: 70px; }
  .persona:first-of-type { margin-top: 56px; }
  .persona .art {
    border-radius: var(--radius); border: 1px solid var(--line); background: var(--paper-warm);
    padding: 34px; min-height: 250px; display: flex; flex-direction: column; justify-content: center; gap: 12px;
  }
  .chat { max-width: 92%; padding: 11px 15px; border-radius: 13px; font-size: 14px; }
  .chat.q { background: var(--ink); color: #fff; align-self: flex-end; border-bottom-right-radius: 4px; }
  .chat.a { background: #fff; border: 1px solid var(--line); color: var(--ink); border-bottom-left-radius: 4px; }
  .persona h3 { font-size: clamp(22px, 3vw, 28px); margin-bottom: 14px; }
  .persona p { color: var(--ink-soft); font-size: 16px; margin-bottom: 12px; }
  .persona ul { list-style: none; margin-top: 6px; }
  .persona li { padding-left: 26px; position: relative; color: var(--ink-soft); font-size: 15px; margin-bottom: 10px; }
  .persona li::before { content: "✓"; position: absolute; left: 0; color: var(--accent); font-weight: 700; }
  .board { background: var(--navy); color: #eef2f7; border: none; }
  .board .boardline { font-family: "SF Mono", ui-monospace, Menlo, monospace; font-size: 15px; }
  .board .circled { position: relative; display: inline-block; padding: 2px 8px; }
  .board .circled::after {
    content: ""; position: absolute; inset: -8px -12px; border: 2.5px solid var(--accent-bright);
    border-radius: 50%; transform: rotate(-3deg);
  }
  .roadstrip {
    margin-top: 70px; border: 1px dashed var(--ink-faint); border-radius: var(--radius);
    padding: 26px 30px; display: flex; gap: 20px; align-items: center; flex-wrap: wrap; justify-content: space-between;
    background: var(--paper-warm);
  }
  .roadstrip p { color: var(--ink-soft); font-size: 15px; max-width: 720px; }
  .roadstrip b { color: var(--ink); }
  @media (max-width: 860px) { .persona { grid-template-columns: 1fr; gap: 28px; } .persona.flip .art { order: -1; } }

  /* ---------- learner model ---------- */
  .learner { background: var(--paper-warm); border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); }
  .learner-grid { display: grid; grid-template-columns: 1.1fr 1fr; gap: 60px; align-items: center; }
  .memory-card {
    background: #fff; border: 1px solid var(--line); border-radius: var(--radius); padding: 26px 28px;
    box-shadow: var(--shadow-sm); font-size: 14px;
  }
  .memory-card .mc-head { font-size: 12px; font-weight: 700; letter-spacing: .06em; text-transform: uppercase; color: var(--accent); margin-bottom: 14px; }
  .memory-card ul { list-style: none; }
  .memory-card li { padding: 9px 0; border-bottom: 1px solid var(--line); color: var(--ink-soft); display: flex; gap: 10px; }
  .memory-card li:last-child { border-bottom: none; }
  .memory-card li::before { content: "◆"; color: var(--accent-bright); font-size: 10px; margin-top: 5px; }
  .memory-card li b { color: var(--ink); font-weight: 600; }
  @media (max-width: 860px) { .learner-grid { grid-template-columns: 1fr; gap: 30px; } }

  /* ---------- privacy ---------- */
  .privacy { background: var(--navy); color: #fff; }
  .privacy .kicker { color: var(--accent-bright); }
  .privacy .lede { color: #b8c2d0; }
  .trustline {
    margin: 30px 0 8px; font-size: clamp(19px, 2.6vw, 24px); font-weight: 600; letter-spacing: -0.01em;
    color: #fff; border-left: 3px solid var(--accent-bright); padding-left: 18px; max-width: 640px; line-height: 1.4;
  }
  .priv-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 22px; margin-top: 44px; }
  .priv { border: 1px solid rgba(255,255,255,.14); border-radius: var(--radius); padding: 26px; background: rgba(255,255,255,.03); }
  .priv h3 { font-size: 17px; margin-bottom: 8px; }
  .priv p { color: #b8c2d0; font-size: 14.5px; }
  @media (max-width: 820px) { .priv-grid { grid-template-columns: 1fr; } }

  /* ---------- pricing ---------- */
  .price-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 22px; margin-top: 52px; align-items: stretch; }
  .price {
    background: #fff; border: 1px solid var(--line); border-radius: var(--radius); padding: 32px 28px;
    display: flex; flex-direction: column;
  }
  .price.pop { border-color: var(--accent-bright); box-shadow: 0 12px 40px rgba(232,89,12,.14); position: relative; }
  .price .pop-badge {
    position: absolute; top: -13px; left: 50%; transform: translateX(-50%);
    background: var(--accent); color: #fff; font-size: 12px; font-weight: 700; letter-spacing: .05em;
    text-transform: uppercase; border-radius: 999px; padding: 4px 14px;
  }
  .price h3 { font-size: 18px; }
  .price .amt { font-size: 40px; font-weight: 700; letter-spacing: -0.03em; margin: 14px 0 2px; }
  .price .amt small { font-size: 15px; font-weight: 500; color: var(--ink-faint); letter-spacing: 0; }
  .price .per { color: var(--ink-faint); font-size: 13.5px; margin-bottom: 20px; }
  .price ul { list-style: none; margin-bottom: 26px; }
  .price li { padding: 7px 0 7px 26px; position: relative; color: var(--ink-soft); font-size: 14.5px; }
  .price li::before { content: "✓"; position: absolute; left: 0; color: var(--accent); font-weight: 700; }
  .price .btn { margin-top: auto; text-align: center; }
  .price-note { text-align: center; color: var(--ink-faint); font-size: 13.5px; margin-top: 26px; }
  @media (max-width: 860px) { .price-grid { grid-template-columns: 1fr; } }

  /* ---------- faq ---------- */
  .faq-list { max-width: 760px; margin: 44px auto 0; }
  details { border-bottom: 1px solid var(--line); padding: 20px 4px; }
  details summary { cursor: pointer; font-weight: 600; font-size: 16.5px; list-style: none; display: flex; justify-content: space-between; align-items: center; }
  details summary::after { content: "+"; color: var(--ink-faint); font-size: 22px; font-weight: 400; }
  details[open] summary::after { content: "–"; }
  details p { margin-top: 12px; color: var(--ink-soft); font-size: 15px; max-width: 660px; }

  /* ---------- pilot cta ---------- */
  .cta-band { text-align: center; background:
    radial-gradient(700px 320px at 50% 120%, var(--accent-soft), transparent 70%), var(--paper); }
  .cta-band .lede { margin: 18px auto 34px; }
  .cta-band .hero-ctas { justify-content: center; }
  .pilot-email { margin-top: 18px; font-size: 15px; color: var(--ink-soft); }
  .pilot-email a { color: var(--accent); font-weight: 600; text-decoration: none; }

  /* ---------- footer ---------- */
  footer { background: var(--navy); color: #b8c2d0; padding: 64px 0 0; }
  .fcols { display: grid; grid-template-columns: 2fr 1fr 1fr 1.2fr; gap: 44px; padding-bottom: 52px; }
  .fbrand .logo { color: #fff; margin-bottom: 14px; }
  .fbrand p { font-size: 14.5px; max-width: 300px; color: #8b98ab; }
  .fcol h4 { color: #fff; font-size: 13px; font-weight: 700; letter-spacing: .07em; text-transform: uppercase; margin-bottom: 16px; }
  .fcol a { display: block; color: #b8c2d0; text-decoration: none; font-size: 14.5px; padding: 5px 0; }
  .fcol a:hover { color: #fff; }
  .fcol .soon { color: #64748b; font-size: 12px; margin-left: 6px; }
  .fbottom {
    border-top: 1px solid rgba(255,255,255,.12); padding: 22px 0 30px;
    display: flex; justify-content: space-between; align-items: center; gap: 14px; flex-wrap: wrap;
    font-size: 13.5px; color: #8b98ab;
  }
  @media (max-width: 860px) { .fcols { grid-template-columns: 1fr 1fr; } }
  @media (max-width: 560px) { .fcols { grid-template-columns: 1fr; } }

  /* ---------- reveal on scroll ---------- */
  .reveal { opacity: 0; transform: translateY(18px); transition: opacity .6s ease, transform .6s ease; }
  .reveal.in { opacity: 1; transform: none; }

  /* ---------- nav "For" dropdown ---------- */
  .drop { position: relative; }
  .drop > a { display: inline-flex; align-items: center; gap: 5px; cursor: default; }
  .drop > a .chev {
    font-size: 13px; color: var(--ink-soft); font-weight: 700; line-height: 1;
    display: inline-block; transition: transform .15s ease;
  }
  .drop:hover > a .chev, .drop:focus-within > a .chev { transform: rotate(180deg); color: var(--accent); }
  .drop-menu { position: absolute; top: 100%; left: 50%; transform: translateX(-50%); padding-top: 12px; display: none; }
  .drop:hover .drop-menu, .drop:focus-within .drop-menu { display: block; }
  .drop-menu-inner {
    background: #fff; border: 1px solid var(--line); border-radius: 12px;
    box-shadow: var(--shadow-lg); padding: 8px; min-width: 250px;
  }
  .drop-menu-inner a { display: block; padding: 10px 14px; border-radius: 8px; font-size: 14.5px; font-weight: 600; color: var(--ink) !important; }
  .drop-menu-inner a:hover { background: var(--paper-warm); }
  .drop-menu-inner a span { display: block; font-size: 12.5px; color: var(--ink-faint); font-weight: 400; margin-top: 1px; }
  .drop-menu-inner a .soon-pill {
    display: inline-block; font-size: 10.5px; font-weight: 700; letter-spacing: .05em; text-transform: uppercase;
    color: var(--accent); background: var(--accent-soft); border-radius: 999px; padding: 1px 8px; margin-left: 7px; vertical-align: 1px;
  }


  /* ---------- classroom projector demo (teachers page) ---------- */
  .pslide {
    background: radial-gradient(900px 460px at 50% -12%, #1e2c44, var(--navy) 72%);
    border-radius: 18px; border: 1px solid rgba(255,255,255,.08);
    padding: 26px 38px 118px; position: relative; overflow: hidden; color: #eef2f7;
    min-height: 440px;
  }
  .pslide-top { display: flex; align-items: center; gap: 18px; font-size: 13px; font-weight: 600; }
  .pclass { letter-spacing: .07em; text-transform: uppercase; font-size: 12px; color: #8b98ab; }
  .plive { display: flex; align-items: center; gap: 7px; color: #b8c2d0; font-size: 12px; letter-spacing: .05em; text-transform: uppercase; }
  .reddot { width: 8px; height: 8px; border-radius: 50%; background: #ff4d4f; animation: blink 1.6s ease infinite; }
  @keyframes blink { 50% { opacity: .2; } }
  .ptimer {
    margin-left: auto; font-family: "SF Mono", ui-monospace, Menlo, monospace; font-size: 15px;
    color: #fff; background: rgba(255,255,255,.09); border: 1px solid rgba(255,255,255,.12);
    padding: 4px 13px; border-radius: 8px; font-variant-numeric: tabular-nums;
  }
  .pslide-kicker {
    margin-top: 40px; text-align: center; color: #8b98ab; font-size: 13px; font-weight: 700;
    letter-spacing: .1em; text-transform: uppercase;
  }
  .pmath {
    text-align: center; margin-top: 14px; font-family: "SF Mono", ui-monospace, Menlo, monospace;
    font-size: clamp(30px, 4.6vw, 46px); color: #fff; letter-spacing: .01em;
  }
  .pproblem { position: relative; display: inline-block; padding: 10px 22px; }
  .pproblem .ring { inset: -6px -10px; width: calc(100% + 20px); height: calc(100% + 12px); }
  .pproblem .ring ellipse { stroke-width: 4; stroke-dasharray: 620; stroke-dashoffset: 620; animation: drawbig 1.2s ease-out .8s forwards; }
  @keyframes drawbig { to { stroke-dashoffset: 0; } }
  .pq { color: #64748b; }
  .hintmode-pill {
    position: absolute; top: 66px; right: 38px; background: var(--accent-bright); color: #fff;
    font-size: 12.5px; font-weight: 700; padding: 7px 14px; border-radius: 999px;
    box-shadow: 0 8px 22px rgba(232,89,12,.4); opacity: 0; animation: pop .4s ease 2.1s forwards;
    letter-spacing: .03em;
  }
  .pstep {
    display: flex; flex-direction: column; gap: 5px; width: fit-content; margin: 18px auto 0;
    border: 1.5px dashed rgba(255,255,255,.3); border-radius: 12px; padding: 12px 20px;
    opacity: 0;
  }
  .pstep.shown { animation: pop .45s ease forwards; }
  .pstep-tag { font-size: 11px; font-weight: 700; letter-spacing: .09em; text-transform: uppercase; color: var(--accent-bright); }
  .pstep-body { font-family: "SF Mono", ui-monospace, Menlo, monospace; font-size: 16.5px; color: #eef2f7; }
  .lower3 {
    position: absolute; left: 0; right: 0; bottom: 0; background: rgba(255,255,255,.97);
    color: var(--ink); padding: 15px 26px; display: flex; align-items: center; gap: 20px;
    border-top: 3px solid var(--accent-bright); transform: translateY(110%);
    animation: slideup .55s cubic-bezier(.2,.8,.25,1) 3s forwards;
  }
  @keyframes slideup { to { transform: none; } }
  .l3-brand { font-size: 11px; font-weight: 800; letter-spacing: .08em; text-transform: uppercase; color: var(--accent); white-space: nowrap; }
  .l3-text { font-size: 14.5px; flex: 1; min-width: 200px; }
  .l3-actions { display: flex; gap: 10px; font-size: 12.5px; font-weight: 600; white-space: nowrap; }
  .l3-actions span { border: 1px solid var(--line); border-radius: 8px; padding: 6px 13px; color: var(--ink-soft); }
  .l3-actions .l3-primary { background: var(--accent); color: #fff; border-color: var(--accent); }
  @media (max-width: 720px) {
    .pslide { padding: 22px 20px 150px; }
    .hintmode-pill { right: 20px; }
    .lower3 { flex-wrap: wrap; gap: 10px; }
  }


  /* ---------- live session: teacher/student view toggle ---------- */
  .viewtoggle {
    display: flex; gap: 4px; background: var(--paper-warm); border: 1px solid var(--line);
    border-radius: 12px; padding: 4px; width: fit-content; margin: 44px auto 28px;
  }
  .viewtoggle button {
    border: 0; background: transparent; padding: 10px 26px; border-radius: 9px;
    font-family: inherit; font-size: 14.5px; font-weight: 600; color: var(--ink-soft); cursor: pointer;
    transition: background .15s ease, color .15s ease;
  }
  .viewtoggle button.active { background: var(--ink); color: #fff; }
  .viewpane { display: none; }
  .viewpane.active { display: block; }
  .view-caption { text-align: center; color: var(--ink-faint); font-size: 14px; margin-top: 18px; }

  .dash {
    max-width: 880px; margin: 0 auto; background: #fff; border: 1px solid var(--line);
    border-radius: 16px; box-shadow: var(--shadow-lg); overflow: hidden;
  }
  .dash-head { display: flex; align-items: center; gap: 12px; padding: 15px 22px; border-bottom: 1px solid var(--line); flex-wrap: wrap; }
  .dash-head .reddot { flex: none; }
  .dash-title { font-weight: 700; font-size: 15px; }
  .dash-sub { color: var(--ink-faint); font-size: 13px; }
  .dash-actions { margin-left: auto; display: flex; gap: 8px; }
  .dash-actions span {
    font-size: 12.5px; font-weight: 600; border: 1px solid var(--line); border-radius: 8px;
    padding: 6px 12px; color: var(--ink-soft);
  }
  .dash-actions .da-primary { background: var(--accent); border-color: var(--accent); color: #fff; }
  .stats { display: grid; grid-template-columns: repeat(3, 1fr); border-bottom: 1px solid var(--line); }
  .stat { padding: 14px 22px; border-right: 1px solid var(--line); }
  .stat:last-child { border-right: 0; }
  .stat b { font-size: 22px; letter-spacing: -0.02em; display: block; }
  .stat span { font-size: 12.5px; color: var(--ink-faint); font-weight: 600; }
  .stat.s-ok b { color: #1a7f4f; }
  .stat.s-hint b { color: #b45309; }
  .stat.s-stuck b { color: #d92d20; }
  .dash-section { padding: 10px 22px 6px; font-size: 11.5px; font-weight: 700; letter-spacing: .08em; text-transform: uppercase; color: var(--ink-faint); }
  .dash-section.urgent { color: #d92d20; }
  .srow {
    display: grid; grid-template-columns: 150px 1fr auto; gap: 16px; align-items: center;
    padding: 11px 22px; border-top: 1px solid var(--line); font-size: 14px;
  }
  .srow .sname { font-weight: 600; }
  .srow .swhere { color: var(--ink-faint); font-size: 12px; display: block; font-weight: 400; }
  .bar { height: 7px; background: var(--paper-warm); border-radius: 999px; overflow: hidden; border: 1px solid var(--line); }
  .bar i { display: block; height: 100%; border-radius: 999px; background: #2ca86b; }
  .bar.b-hint i { background: #f2a33c; }
  .bar.b-stuck i { background: #ef6a5a; }
  .st { font-size: 12px; font-weight: 700; border-radius: 999px; padding: 4px 11px; white-space: nowrap; }
  .st-ok { background: #e8f6ee; color: #1a7f4f; }
  .st-hint { background: #fdf1df; color: #b45309; }
  .st-stuck { background: #fdebe9; color: #d92d20; }
  .srow.more { color: var(--ink-faint); font-size: 13px; display: block; text-align: center; padding: 12px; }
  .insight {
    margin: 14px 18px 18px; background: var(--accent-soft); border: 1px solid #ffd9b8;
    border-radius: 12px; padding: 14px 18px; display: flex; gap: 14px; align-items: center; flex-wrap: wrap;
  }
  .insight .ib { font-size: 13.5px; color: var(--ink); flex: 1; min-width: 240px; }
  .insight .ib b { color: var(--accent); }
  .insight span.da-primary {
    font-size: 12.5px; font-weight: 700; background: var(--accent); color: #fff;
    border-radius: 8px; padding: 7px 14px; white-space: nowrap;
  }

  .sview { max-width: 620px; margin: 0 auto; }
  .sview .doc { max-width: none; }
  .sview-meta {
    display: flex; gap: 10px; justify-content: center; flex-wrap: wrap; margin-top: 16px;
  }
  .sview-meta span {
    font-size: 12.5px; font-weight: 600; color: var(--ink-soft); background: var(--paper-warm);
    border: 1px solid var(--line); border-radius: 999px; padding: 6px 14px;
  }
  .sview-meta span.rule { color: var(--accent); background: var(--accent-soft); border-color: #ffd9b8; }
  @media (max-width: 680px) {
    .srow { grid-template-columns: 110px 1fr; }
    .srow .st { display: none; }
    .stats { grid-template-columns: 1fr; }
    .stat { border-right: 0; border-bottom: 1px solid var(--line); }
  }


  /* ---------- interactive demo: shared ---------- */
  .l3-actions button, .mini-btn, .votebar button {
    font-family: inherit; cursor: pointer; transition: transform .1s ease, background .15s ease;
  }
  .l3-actions button {
    border: 1px solid var(--line); background: #fff; border-radius: 8px; padding: 6px 13px;
    color: var(--ink-soft); font-size: 12.5px; font-weight: 600;
  }
  .l3-actions button.l3-primary { background: var(--accent); color: #fff; border-color: var(--accent); }
  .l3-actions button:hover:not(:disabled) { transform: translateY(-1px); }
  .l3-actions button:disabled { opacity: .45; cursor: default; }
  .toast {
    position: fixed; left: 50%; bottom: 34px; transform: translateX(-50%) translateY(20px);
    background: var(--ink); color: #fff; font-size: 14px; font-weight: 600;
    padding: 12px 22px; border-radius: 12px; box-shadow: var(--shadow-lg);
    opacity: 0; transition: opacity .25s ease, transform .25s ease; z-index: 90; pointer-events: none;
    max-width: 90vw; text-align: center;
  }
  .toast.show { opacity: 1; transform: translateX(-50%) translateY(0); }
  .hvpane { display: none; }
  .hvpane.active { display: block; }
  .hero .viewtoggle { margin: 40px auto 22px; }

  /* ---------- presenter console (teacher's mac) ---------- */
  .console {
    max-width: 860px; margin: 0 auto; background: #fff; border: 1px solid var(--line);
    border-radius: 16px; box-shadow: var(--shadow-lg); overflow: hidden;
  }
  .console-head {
    display: flex; align-items: center; gap: 10px; padding: 13px 22px; border-bottom: 1px solid var(--line);
    font-size: 13px; font-weight: 700; color: var(--ink-soft); letter-spacing: .04em; text-transform: uppercase;
  }
  .console-head .ptimer { margin-left: auto; color: var(--ink); background: var(--paper-warm); border-color: var(--line); }
  .console-grid { display: grid; grid-template-columns: 1fr 1.4fr; gap: 0; }
  .mini-slide {
    margin: 22px; border-radius: 12px; background: radial-gradient(300px 160px at 50% -10%, #1e2c44, var(--navy) 75%);
    color: #fff; display: flex; flex-direction: column; align-items: center; justify-content: center;
    font-family: "SF Mono", ui-monospace, Menlo, monospace; font-size: 22px; min-height: 170px; gap: 10px;
  }
  .mini-slide span { font-family: -apple-system, BlinkMacSystemFont, sans-serif; font-size: 11px; color: #8b98ab; letter-spacing: .08em; text-transform: uppercase; }
  .pulse { padding: 22px 24px 10px 4px; }
  .pulse-title { font-size: 12px; font-weight: 700; letter-spacing: .07em; text-transform: uppercase; color: var(--ink-faint); margin-bottom: 14px; }
  .prow { display: grid; grid-template-columns: 74px 1fr 34px; gap: 12px; align-items: center; margin-bottom: 11px; font-size: 13.5px; font-weight: 600; }
  .prow .bar { height: 9px; }
  .prow b { font-variant-numeric: tabular-nums; text-align: right; }
  .prow.p-got { color: #1a7f4f; }
  .prow.p-shaky { color: #b45309; }
  .prow.p-lost { color: #d92d20; }
  .pulse-note {
    margin-top: 14px; font-size: 13px; color: var(--ink-soft); background: var(--paper-warm);
    border: 1px solid var(--line); border-radius: 10px; padding: 10px 14px;
  }
  .nexthint {
    display: flex; align-items: center; gap: 18px; margin: 10px 22px 22px; padding: 14px 18px;
    background: var(--accent-soft); border: 1px solid #ffd9b8; border-radius: 12px; flex-wrap: wrap;
  }
  .nexthint .nh-tag { display: block; font-size: 11px; font-weight: 800; letter-spacing: .08em; text-transform: uppercase; color: var(--accent); margin-bottom: 4px; }
  .nexthint p { font-size: 13.5px; color: var(--ink); flex: 1; min-width: 220px; }
  .nexthint > div { flex: 1; min-width: 240px; }
  .nexthint .btn { white-space: nowrap; }
  .nexthint .btn:disabled { opacity: .5; cursor: default; transform: none; box-shadow: none; }
  @media (max-width: 720px) { .console-grid { grid-template-columns: 1fr; } .pulse { padding: 0 22px 10px; } }

  /* ---------- student seat ---------- */
  .seat { max-width: 560px; margin: 0 auto; }
  .seat .doc { max-width: none; }
  .seat-now { font-size: 11.5px; font-weight: 700; letter-spacing: .08em; text-transform: uppercase; color: var(--ink-faint); margin: 4px 0 8px; }
  .votebar { display: flex; gap: 10px; justify-content: center; margin-top: 18px; flex-wrap: wrap; }
  .votebar button {
    border: 1.5px solid var(--line); background: #fff; border-radius: 12px; padding: 12px 22px;
    font-size: 15px; font-weight: 600; color: var(--ink);
  }
  .votebar button:hover { transform: translateY(-1px); border-color: var(--ink-faint); }
  .votebar button.picked { border-color: var(--accent); background: var(--accent-soft); color: var(--accent); }

  /* ---------- interactive dashboard rows ---------- */
  .srow.clickable { cursor: pointer; }
  .srow.clickable:hover { background: var(--paper-warm); }
  .sdetail { display: none; padding: 4px 22px 16px; border-top: 1px dashed var(--line); background: var(--paper-warm); }
  .sdetail.open { display: block; }
  .sdetail p { font-size: 13.5px; color: var(--ink-soft); margin: 10px 0 12px; }
  .mini-btn {
    border: 1px solid var(--line); background: #fff; border-radius: 8px; padding: 6px 13px;
    color: var(--ink-soft); font-size: 12.5px; font-weight: 600; margin-right: 8px;
  }
  .mini-btn:hover { border-color: var(--accent); color: var(--accent); }
  .dash-actions span, .insight .da-primary, .tp-input span:last-child { cursor: pointer; }
  .dash.paused .srow, .dash.paused .stats { opacity: .45; }