:root{
      --bg:#fffbe6;
      --card:#ffffff;
      --ink:#163028;
      --muted:#53645f;
      --brand:#0f3d2e;
      --brand-2:#1f6d4f;
      --accent:#f3b63f;
      --accent-2:#e67e22;
      --good:#237a3b;
      --soft:#eef5f1;
      --shadow:0 10px 30px rgba(15,61,46,.10);
      --radius:22px;
      --footer-green:#1b4332;
    }

    *{box-sizing:border-box}
    html{scroll-behavior:smooth}
    body{
      margin:0;
      font-family: Arial, Helvetica, sans-serif;
      background:linear-gradient(180deg,#fffbe6 0%, #f8f4df 100%);
      color:var(--ink);
      line-height:1.6;
    }

    .wrap{max-width:1160px;margin:0 auto;padding:18px}

    header{
      position:relative;
      overflow:hidden;
      background:linear-gradient(135deg,var(--brand) 0%, #174f3c 52%, #2c7a5d 100%);
      color:#fff;
      padding:28px 0 46px;
      box-shadow:0 8px 26px rgba(0,0,0,.15);
    }

    header::after{
      content:"";
      position:absolute;
      inset:auto -80px -120px auto;
      width:340px;height:340px;
      background:radial-gradient(circle, rgba(255,255,255,.22), transparent 65%);
      border-radius:50%;
    }

    .topbar{display:flex;align-items:center;gap:14px;flex-wrap:wrap;margin-bottom:26px}
    .logo-box{
      width:72px;height:72px;border-radius:18px;flex:0 0 72px;
      background:rgba(255,255,255,.10);border:1px solid rgba(255,255,255,.18);
      display:grid;place-items:center;overflow:hidden;backdrop-filter: blur(4px);
    }
    .logo-box img{max-width:100%;max-height:100%;display:block}
    .logo-fallback{font-size:28px}

    .eyebrow{
      display:inline-block;background:rgba(255,255,255,.14);border:1px solid rgba(255,255,255,.18);
      padding:7px 12px;border-radius:999px;font-weight:700;letter-spacing:.2px;margin-bottom:10px;font-size:.95rem;
    }

    h1{margin:0 0 12px;font-size:clamp(2rem, 4vw, 3.2rem);line-height:1.1}
    .lead{max-width:900px;font-size:1.08rem;color:#eef8f2;margin-bottom:18px}

    .hero-grid{display:grid;grid-template-columns:1.5fr .95fr;gap:18px;align-items:start}
    .hero-card,.panel,.exercise,.card,.tip,.mini,.quote-box,.table-box,.rule-card,.level-box{
      background:var(--card);border-radius:var(--radius);box-shadow:var(--shadow);border:1px solid rgba(15,61,46,.08);
    }
    .hero-card{padding:22px;background:rgba(255,255,255,.10);border-color:rgba(255,255,255,.18);box-shadow:none}
    .hero-card h2{margin:0 0 8px;font-size:1.15rem}
    .hero-card p{margin:0;color:#eef8f2}
    .hero-actions{display:flex;gap:12px;flex-wrap:wrap;margin-top:18px}

    .btn{
      display:inline-flex;align-items:center;justify-content:center;gap:8px;padding:12px 18px;border-radius:14px;
      text-decoration:none;border:none;cursor:pointer;font-weight:700;font-size:1rem;
      transition:transform .18s ease, box-shadow .18s ease, filter .18s ease;
    }
    .btn:hover{transform:translateY(-2px);filter:brightness(1.02)}
    .btn-main{background:#fffbe6;color:var(--brand);box-shadow:0 8px 18px rgba(0,0,0,.12)}
    .btn-outline{background:transparent;color:#fff;border:1px solid rgba(255,255,255,.35)}

    .hero-side{display:grid;gap:12px}
    .hero-side .mini{padding:16px;background:rgba(255,255,255,.10);color:#fff;border-color:rgba(255,255,255,.18);box-shadow:none}
    .hero-side strong{display:block;font-size:1.08rem}

    nav.quick-nav{margin-top:-24px;position:relative;z-index:2}
    .quick-nav .panel{padding:16px;display:flex;gap:10px;flex-wrap:wrap;justify-content:center}
    .chip{padding:9px 12px;background:#f3f8f5;color:var(--brand);border-radius:999px;text-decoration:none;font-weight:700;font-size:.95rem;border:1px solid rgba(15,61,46,.08)}

    main{padding:28px 0 8px}
    section{margin:22px 0 30px}
    .section-head{margin-bottom:14px}
    .section-head h2{margin:0 0 6px;font-size:clamp(1.45rem, 2.2vw, 2rem);color:var(--brand)}
    .section-head p{margin:0;color:var(--muted)}

    .grid-2{display:grid;grid-template-columns:1fr 1fr;gap:18px}
    .grid-3{display:grid;grid-template-columns:repeat(3,1fr);gap:18px}
    .rule-grid{display:grid;grid-template-columns:repeat(2,1fr);gap:18px}
    .panel,.exercise,.quote-box,.table-box,.rule-card,.level-box{padding:22px}
    .panel h3,.exercise h3,.quote-box h3,.table-box h3,.rule-card h3,.level-box h3{margin:0 0 12px;color:var(--brand);font-size:1.15rem}

    .formula-block{
      background:#f7fbf8;border:1px dashed rgba(15,61,46,.18);border-radius:18px;padding:18px;
      font-size:1.08rem;text-align:center;margin:12px 0;
    }
    .formula-big{font-size:1.35rem;font-weight:700;color:var(--brand)}
    .math{font-size:1.06em}
    .katex{font-size:1.04em}
    .formula-big .katex{font-size:1.16em}
    .formula-block .katex-display,.result .katex-display,.step .katex-display{margin:.35em 0}
    .math-display{margin:10px 0;overflow-x:auto}

    .panel-highlight{
      background:linear-gradient(135deg, #fff4cf 0%, #fff9e8 100%);
      border-left:6px solid var(--accent);
      padding:20px 22px;border-radius:20px;box-shadow:var(--shadow);
      font-weight:700;font-size:1.16rem;color:var(--brand);
    }

    .steps{display:grid;gap:12px}
    .step{padding:14px 16px;border-radius:16px;background:#fafdfb;border:1px solid rgba(15,61,46,.08)}
    .step strong{color:var(--brand)}

    .result{
      margin-top:12px;padding:14px 16px;border-radius:16px;background:#f3f8f5;border-left:5px solid var(--brand-2);font-weight:700;
    }
    .result.good{border-left-color:var(--good);background:#eef8f1}
    .result.warn{border-left-color:var(--accent-2);background:#fff6ea}

    .badge-row{display:flex;gap:10px;flex-wrap:wrap;margin-top:12px}
    .badge{background:#eff7f2;color:var(--brand);padding:8px 11px;border-radius:999px;font-weight:700;font-size:.92rem}

    .rule-card{
      background:linear-gradient(180deg,#ffffff 0%, #fbfdfc 100%);
    }
    .rule-card p{margin:0;color:var(--muted)}

    details.tip{padding:16px 18px;margin-bottom:12px;background:#fff}
    details.tip summary{cursor:pointer;font-weight:700;color:var(--brand);list-style:none}
    details.tip summary::-webkit-details-marker{display:none}
    details.tip[open]{background:#fcfefc}

    .level-box{
      border-top:5px solid var(--brand-2);
      background:linear-gradient(180deg,#ffffff 0%, #fbfcfb 100%);
    }

    ol.exercise-list{margin:0;padding-left:22px}
    ol.exercise-list li{margin:8px 0 12px;color:var(--ink)}
    ol.exercise-list li strong{color:var(--brand)}

    .table-box table{width:100%;border-collapse:collapse;border-radius:16px;overflow:hidden;background:#fff}
    .table-box th,.table-box td{padding:12px 10px;border-bottom:1px solid #ecf0ee;text-align:left;vertical-align:top}
    .table-box th{background:#f3f8f5;color:var(--brand)}
    .table-box tr:last-child td{border-bottom:none}

    .trainer-toolbar{display:flex;gap:10px;flex-wrap:wrap;margin:16px 0 20px}
    .trainer-note{margin-top:12px;color:var(--muted)}
    .level-cluster{margin:20px 0 28px}
    .cluster-head{display:flex;align-items:center;justify-content:space-between;gap:12px;flex-wrap:wrap;margin-bottom:14px}
    .cluster-head h3{margin:0;color:var(--brand);font-size:1.18rem}
    .cluster-head p{margin:0;color:var(--muted)}
    .trainer-grid{display:grid;grid-template-columns:repeat(2,1fr);gap:18px}
    .exercise-card-interactive{background:linear-gradient(180deg,#ffffff 0%, #fbfdfc 100%);border:1px solid rgba(15,61,46,.08);border-radius:22px;box-shadow:var(--shadow);padding:20px;}
    .card-top{display:flex;align-items:center;justify-content:space-between;gap:12px;flex-wrap:wrap;margin-bottom:8px}
    .card-top h4{margin:0;color:var(--brand);font-size:1.08rem}
    .level-tag{display:inline-flex;align-items:center;gap:8px;padding:7px 11px;border-radius:999px;font-weight:700;font-size:.9rem}
    .level-1{background:#eff7f2;color:#17633f}
    .level-2{background:#eef4ff;color:#2747a3}
    .level-3{background:#fff3e8;color:#a45418}
    .level-4{background:#f7ecff;color:#6f2e9b}
    .toggle-row{display:flex;gap:10px;flex-wrap:wrap;margin-top:14px}
    .toggle-btn{padding:10px 14px;font-size:.96rem}
    .hidden-panel{display:none;margin-top:14px;padding:14px 16px;border-radius:16px;border:1px solid rgba(15,61,46,.10);background:#fcfefc}
    .hidden-panel.open{display:block}
    .hint-panel{background:#eef8f1;border-left:5px solid var(--good)}
    .next-panel{background:#eef4ff;border-left:5px solid #3d5af1}
    .development-panel{background:#fffaf1;border-left:5px solid var(--accent-2)}
    .development-panel .step{background:#fffdf8}
    .final-panel{background:#f5efff;border-left:5px solid #7b3fe4}
    .gabarito-wrap details{background:#fff}
    .resolved-toolbar{display:flex;gap:10px;flex-wrap:wrap;margin:16px 0 18px}
    details.resolved-item{padding:0;overflow:hidden;background:linear-gradient(180deg,#ffffff 0%, #fbfdfc 100%)}
    details.resolved-item summary{list-style:none;cursor:pointer;padding:18px 20px;display:flex;justify-content:space-between;align-items:flex-start;gap:14px}
    details.resolved-item summary::-webkit-details-marker{display:none}
    .resolved-summary-main h3{margin:0 0 6px;color:var(--brand);font-size:1.08rem}
    .resolved-summary-main p{margin:0;color:var(--muted)}
    .resolved-meta{display:flex;gap:8px;flex-wrap:wrap;align-items:center;justify-content:flex-end}
    .resolved-badge{display:inline-flex;align-items:center;justify-content:center;padding:7px 11px;border-radius:999px;background:#edf5f1;color:var(--brand);font-weight:700;font-size:.9rem;border:1px solid rgba(15,61,46,.08)}
    .resolved-chevron{font-size:1.05rem;transition:transform .22s ease;color:var(--brand)}
    details.resolved-item[open] .resolved-chevron{transform:rotate(180deg)}
    .resolved-content{padding:0 20px 20px}
    .resolved-content > p{margin-top:0}
    

    .footer-action{text-align:center;margin-top:22px;padding:0 16px}
    .footer-links{display:flex;gap:12px;justify-content:center;flex-wrap:wrap;max-width:980px;margin:0 auto;}
    .btn-voltar-aplicacoes{
      display:inline-block;padding:13px 24px;border-radius:10px;text-decoration:none;font-weight:700;transition:all .25s ease;
      box-shadow:0 2px 8px rgba(0,0,0,.06);background:#ffffff;color:var(--footer-green);border:2px solid var(--footer-green);margin-bottom:20px;
    }
    .btn-voltar-aplicacoes:hover{background:var(--footer-green);color:#ffffff;transform:translateY(-2px)}
    .rodape-oficial{background:var(--footer-green);color:#ffffff;text-align:center;padding:22px 16px;margin-top:0;border-top:1px solid #163828}
    .rodape-conteudo{max-width:980px;margin:0 auto}
    .rodape-conteudo p{margin:6px 0;font-size:.95rem;line-height:1.55}

    @media (max-width: 920px){
      .hero-grid,.grid-2,.grid-3,.rule-grid,.trainer-grid{grid-template-columns:1fr}
    }

    @media (max-width: 640px){
      .wrap{padding:14px}
      .panel,.exercise,.quote-box,.table-box,.rule-card,.level-box{padding:18px}
      .hero-card{padding:18px}
      .btn{width:100%}
      .hero-actions .btn{justify-content:center}
      .btn-voltar-aplicacoes{width:100%;max-width:360px}
    }
  /* =====================================================
   Vídeo introdutório — Desmistificando a Derivada
   ===================================================== */
   .video-derivada-destaque {
  max-width: 980px;
  margin: 34px auto;
  padding: 28px;
  background: linear-gradient(135deg, #fffdf2, #f7f0ff);
  border: 2px solid #e2cf89;
  border-radius: 24px;
  box-shadow: 0 12px 30px rgba(0, 0, 0, 0.12);
  text-align: center;
}

.video-derivada-destaque .video-selo {
  display: inline-block;
  margin-bottom: 10px;
  padding: 7px 14px;
  border-radius: 999px;
  background: #4b2e83;
  color: #ffffff;
  font-weight: 700;
  font-size: 0.95rem;
}

.video-derivada-destaque h2 {
  margin: 8px 0 14px;
  color: #3b2567;
  font-size: clamp(1.6rem, 3vw, 2.25rem);
}

.video-derivada-destaque p {
  max-width: 820px;
  margin: 8px auto;
  color: #333333;
  font-size: 1.06rem;
  line-height: 1.65;
}

.video-wrapper {
  position: relative;
  width: 100%;
  max-width: 900px;
  margin: 24px auto 0;
  padding-bottom: 56.25%;
  height: 0;
  overflow: hidden;
  border-radius: 18px;
  background: #000;
  box-shadow: 0 10px 28px rgba(0, 0, 0, 0.22);
}

.video-wrapper iframe {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
}

.video-acoes {
  margin-top: 22px;
}

.btn-youtube {
  display: inline-block;
  padding: 13px 24px;
  border-radius: 999px;
  background: #4b2e83;
  color: #ffffff;
  text-decoration: none;
  font-weight: 800;
  box-shadow: 0 8px 18px rgba(75, 46, 131, 0.25);
  transition: transform 0.2s ease, filter 0.2s ease;
}

.btn-youtube:hover {
  transform: translateY(-2px);
  filter: brightness(1.08);
}

@media (max-width: 700px) {
  .video-derivada-destaque {
    padding: 20px;
    margin: 24px 12px;
  }

  .video-derivada-destaque p {
    font-size: 1rem;
  }

  .btn-youtube {
    width: 100%;
    max-width: 320px;
  }
}