/* Extracted from landing_version_gemini_V16.html. Preserve visual parity when editing. */
/* VARIABLES GLOBALES - THÈME CLAIR (Landing) */
    :root {
      --bg: #f8fafc;
      --bg-surface: #ffffff;
      --ink: #0f172a;
      --ink-soft: #475569;
      --ink-faint: #94a3b8;
      --primary: #2563eb;
      --primary-2: #4f46e5;
      --primary-hover: #1d4ed8;
      --accent: #0ea5e9;
      --border: #e2e8f0;
      --border-light: #f1f5f9;
      --green: #10b981;
      --red: #ef4444;
      --radius: 24px;
      --shadow-sm: 0 4px 6px -1px rgba(0,0,0,0.05);
      --shadow-lg: 0 20px 40px -10px rgba(15,23,42,0.1);
      --shell: 1200px;
      --font: 'Inter', system-ui, sans-serif;

      /* VARIABLES APP (Mockups fidèles aux images) */
      --app-bg: #0b0f19;
      --app-panel: #111827;
      --app-card: #1f2937;
      --app-border: #374151;
      --app-text: #f3f4f6;
      --app-text-soft: #9ca3af;
      --app-green: #10b981;
      --app-green-bg: rgba(16, 185, 129, 0.15);
      --app-red: #f43f5e;
      --app-red-bg: rgba(244, 63, 94, 0.15);
    }

    * { box-sizing: border-box; margin: 0; padding: 0; }
    html { scroll-behavior: smooth; background: var(--bg-surface); font-size: 16px; overflow-x: clip; }
    body { width: 100%; overflow-x: clip; background: var(--bg-surface); font-family: var(--font); color: var(--ink); line-height: 1.5; -webkit-font-smoothing: antialiased; }
    a { color: inherit; text-decoration: none; }
    button { font: inherit; cursor: pointer; border: none; background: none; }
    img { max-width: 100%; display: block; }
    ul { list-style: none; }

    @supports not (overflow: clip) {
      html,
      body { overflow-x: hidden; }
    }

    /* LAYOUT & RYTHME VERTICAL */
    .shell { max-width: var(--shell); margin: 0 auto; padding: 0 20px; }
    .section { position: relative; padding: 112px 0; }
    .section-alt { background: var(--bg); border-top: 1px solid rgba(226, 232, 240, 0.6); border-bottom: 1px solid rgba(226, 232, 240, 0.6); }
    .section-head { text-align: center; max-width: 720px; margin: 0 auto 64px; }
    .section-head h2 { margin-bottom: 20px; font-size: clamp(2rem, 4vw, 2.75rem); font-weight: 800; line-height: 1.15; letter-spacing: -0.02em; }
    .section-head .lead { margin: 0 auto; }

    /* TYPOGRAPHIE */
    .eyebrow-row { display: flex; justify-content: center; margin-bottom: 18px; }
    .badge { display: inline-flex; align-items: center; gap: 10px; padding: 9px 14px; border-radius: 999px; background: rgba(37, 99, 235, 0.08); border: 1px solid rgba(37, 99, 235, 0.12); color: var(--primary); font-weight: 800; font-size: 0.84rem; text-transform: uppercase; letter-spacing: 0.07em; box-shadow: inset 0 1px 0 rgba(255,255,255,0.85); }
    .badge::before { content: ""; width: 8px; height: 8px; border-radius: 50%; background: linear-gradient(135deg, var(--primary), var(--accent)); box-shadow: 0 0 0 5px rgba(37, 99, 235, 0.12); }
    h1 { font-size: clamp(2.5rem, 5vw, 4rem); font-weight: 800; line-height: 1.1; letter-spacing: -0.03em; margin-bottom: 24px; }
    h2 { font-size: clamp(2rem, 4vw, 2.75rem); font-weight: 800; line-height: 1.15; letter-spacing: -0.02em; margin-bottom: 16px; }
    .lead { font-size: clamp(1.1rem, 2vw, 1.25rem); color: var(--ink-soft); margin-bottom: 32px; max-width: 65ch; }
    .text-gradient { background: linear-gradient(135deg, var(--primary), var(--accent)); -webkit-background-clip: text; -webkit-text-fill-color: transparent; }

    /* BOUTONS */
    .btn { display: inline-flex; justify-content: center; align-items: center; gap: 8px; height: 54px; padding: 0 28px; border-radius: 99px; font-weight: 700; font-size: 1.05rem; transition: all 0.2s; white-space: nowrap; }
    .btn-primary { background: var(--primary); color: white; box-shadow: 0 8px 20px rgba(37,99,235,0.25); }
    .btn-primary:hover { background: var(--primary-hover); transform: translateY(-2px); box-shadow: 0 12px 24px rgba(37,99,235,0.3); }
    .btn-secondary { background: white; color: var(--ink); border: 2px solid var(--border); }
    .btn-secondary:hover { border-color: var(--primary); color: var(--primary); }
    .btn-sm { min-height: 46px; height: 46px; padding: 0 20px; font-size: 0.95rem; }

    /* NAVBAR */
    .navbar { position: fixed; top: 16px; left: 0; width: 100%; z-index: 100; transition: transform 0.22s ease, opacity 0.22s ease; }
    .nav-shell { width: min(1280px, calc(100% - 28px)); margin: 0 auto; padding: 12px 18px; border-radius: 24px; display: flex; align-items: center; justify-content: space-between; gap: 24px; background: rgba(255,255,255,0.68); border: 1px solid rgba(255,255,255,0.85); box-shadow: 0 12px 44px rgba(15, 23, 42, 0.08); backdrop-filter: blur(18px); -webkit-backdrop-filter: blur(18px); }
    .navbar.scrolled .nav-shell { background: rgba(255,255,255,0.82); box-shadow: 0 16px 48px rgba(15, 23, 42, 0.12); }
    .brand { display: inline-flex; align-items: center; gap: 14px; min-width: 0; }
    .brand-mark { width: 42px; height: 42px; border-radius: 14px; display: grid; place-items: center; font-weight: 900; font-size: 0.95rem; color: white; background: linear-gradient(135deg, var(--primary), var(--primary-2) 55%, var(--accent)); box-shadow: 0 14px 28px rgba(79, 70, 229, 0.25); flex-shrink: 0; }
    .brand-mark--image { display: block; object-fit: contain; background: transparent; }
    .brand-copy { display: flex; flex-direction: column; justify-content: center; min-width: 0; }
    .brand-copy strong { font-size: 1.15rem; color: var(--ink); line-height: 1; letter-spacing: 0; }
    .nav-links { display: flex; align-items: center; gap: 8px; padding: 6px; background: rgba(255,255,255,0.7); border: 1px solid rgba(15,23,42,0.05); border-radius: 999px; box-shadow: inset 0 1px 0 rgba(255,255,255,0.92); }
    .nav-links a { padding: 10px 14px; border-radius: 999px; font-size: 0.95rem; font-weight: 700; color: var(--ink-soft); transition: background 0.2s ease, color 0.2s ease; }
    .nav-links a:hover { background: rgba(37, 99, 235, 0.08); color: var(--primary); }
    .nav-actions { display: flex; align-items: center; gap: 12px; flex-shrink: 0; }
    .nav-login { padding: 8px 12px; color: var(--ink-soft); font-size: 0.95rem; font-weight: 700; transition: color 0.2s ease; }
    .nav-login:hover { color: var(--primary); }

    /* HERO */
    .hero { padding: 132px 0 112px; background: radial-gradient(circle at top, rgba(37,99,235,0.08), transparent 60%), var(--bg); overflow: hidden; }
    .hero-grid { display: grid; grid-template-columns: minmax(0, 0.92fr) minmax(420px, 1.08fr); gap: 56px; align-items: center; }
    .hero .lead { margin: 0 0 28px; }
    .hero-trust { color: var(--ink-soft); font-weight: 650; margin-bottom: 28px; }
    .cta-group { display: flex; gap: 16px; margin-bottom: 34px; flex-wrap: wrap; }

    .hero-media { position: relative; min-height: 560px; }
    .browser-shot { position: relative; overflow: hidden; border: 1px solid rgba(15, 23, 42, 0.1); border-radius: 20px; background: #ffffff; box-shadow: var(--shadow-lg); }
    .browser-shot::before { content: ''; display: block; height: 34px; background: linear-gradient(180deg, #f8fafc, #eef2f7); border-bottom: 1px solid var(--border); }
    .browser-shot::after { content: ''; position: absolute; top: 13px; left: 16px; width: 8px; height: 8px; border-radius: 50%; background: #ef4444; box-shadow: 14px 0 #f59e0b, 28px 0 #10b981; }
    .browser-shot img { width: 100%; height: auto; }
    .browser-label { padding: 10px 14px; color: var(--ink-soft); font-size: 0.86rem; font-weight: 700; background: rgba(248, 250, 252, 0.96); border-top: 1px solid var(--border); }

    /* =========================================================
       HERO MEDIA SHOWCASE - DISPOSITION ÉVENTAIL (PREMIUM)
       ========================================================= */
    .hero-media.stack-container {
      min-height: 560px;
      display: flex;
      align-items: center;
      justify-content: center;
      perspective: 1400px;
      isolation: isolate;
      position: relative;
    }

    .stack-card {
      position: absolute;
      width: min(620px, 85%);
      max-width: 620px;
      cursor: pointer;
      transform-origin: 50% 100%;
      transform-style: preserve-3d;
      will-change: transform, opacity, z-index;
      transition: transform 0.85s cubic-bezier(0.25, 1, 0.35, 1),
                  opacity 0.7s ease,
                  box-shadow 0.7s ease,
                  border-color 0.7s ease;
    }

    .stack-card .browser-label {
      min-height: 54px;
      display: flex;
      align-items: center;
      transition: color 0.3s ease, background 0.3s ease;
    }

    .stack-card.is-active,
    .stack-card.pos-1 {
      z-index: 4;
      opacity: 1;
      transform: translate3d(0, -5%, 80px) scale(1) rotate(0deg);
      border-color: rgba(37, 99, 235, 0.25);
      box-shadow: 0 40px 80px -20px rgba(15, 23, 42, 0.4);
    }

    .stack-card.is-next,
    .stack-card.pos-2 {
      z-index: 3;
      opacity: 0.65;
      transform: translate3d(32%, 2%, -60px) scale(0.85) rotate(8deg);
      box-shadow: 0 20px 40px rgba(15, 23, 42, 0.15);
    }

    .stack-card.is-prev,
    .stack-card.pos-3 {
      z-index: 2;
      opacity: 0.65;
      transform: translate3d(-32%, 2%, -60px) scale(0.85) rotate(-8deg);
      box-shadow: 0 20px 40px rgba(15, 23, 42, 0.15);
    }

    .stack-card.is-active .browser-label,
    .stack-card.pos-1 .browser-label { color: var(--ink); background: #ffffff; }

    .stack-card.is-active:hover {
      transform: translate3d(0, -8%, 100px) scale(1.02) rotate(0deg);
      box-shadow: 0 50px 100px -20px rgba(15, 23, 42, 0.45);
    }

    .stack-card.is-next:hover {
      opacity: 0.9;
      transform: translate3d(36%, 0%, -40px) scale(0.88) rotate(10deg);
    }

    .stack-card.is-prev:hover {
      opacity: 0.9;
      transform: translate3d(-36%, 0%, -40px) scale(0.88) rotate(-10deg);
    }

    .stack-card:focus-visible { outline: 3px solid rgba(37, 99, 235, 0.45); outline-offset: 6px; }
    .stack-dots {
      position: absolute;
      left: 50%;
      bottom: 18px;
      z-index: 8;
      display: grid;
      grid-template-columns: repeat(3, 36px);
      align-items: center;
      justify-content: center;
      gap: 2px;
      padding: 8px;
      border: 1px solid rgba(226, 232, 240, 0.9);
      border-radius: 999px;
      background: rgba(255, 255, 255, 0.78);
      box-shadow: 0 12px 30px rgba(15, 23, 42, 0.12);
      transform: translateX(-50%);
      backdrop-filter: blur(14px);
      -webkit-backdrop-filter: blur(14px);
    }
    .stack-dot {
      position: relative;
      width: 36px;
      height: 24px;
      border-radius: 999px;
      display: grid;
      place-items: center;
    }
    .stack-dot::before {
      content: '';
      width: 8px;
      height: 8px;
      border-radius: 999px;
      background: #cbd5e1;
      transition: width 0.28s cubic-bezier(0.16, 1, 0.3, 1), background 0.28s ease, box-shadow 0.28s ease;
    }
    .stack-dot:hover::before { background: #94a3b8; }
    .stack-dot.is-active::before {
      width: 28px;
      background: linear-gradient(135deg, var(--primary), var(--accent));
      box-shadow: 0 5px 14px rgba(37, 99, 235, 0.28);
    }
    .stack-dot:focus-visible { outline: 3px solid rgba(37, 99, 235, 0.35); outline-offset: 3px; }

    /* SECTION ÉPREUVE - BENTO GRID */
    .official-bento { display: grid; grid-template-columns: repeat(6, 1fr); gap: 24px; margin-top: 0; }
    .bento-card { position: relative; overflow: hidden; padding: 36px 32px; border: 1px solid rgba(226, 232, 240, 0.8); border-radius: 28px; background: #ffffff; box-shadow: 0 4px 20px rgba(15, 23, 42, 0.03); transition: transform 0.4s cubic-bezier(0.25, 1, 0.35, 1), box-shadow 0.4s cubic-bezier(0.25, 1, 0.35, 1), border-color 0.4s ease; will-change: transform, box-shadow; }
    .bento-card::after { content: ''; position: absolute; top: 0; right: 0; width: 180px; height: 180px; border-radius: 0 28px 0 100%; background: radial-gradient(circle at top right, rgba(37, 99, 235, 0.06), transparent 70%); pointer-events: none; transition: opacity 0.4s ease; }
    .bento-card:hover { transform: translateY(-6px); border-color: rgba(37, 99, 235, 0.3); box-shadow: 0 24px 48px -12px rgba(37, 99, 235, 0.15); }
    .bento-card:hover::after { opacity: 0.8; }
    .bento-card.top-row { grid-column: span 2; }
    .bento-card.bottom-row { grid-column: span 3; }
    .bento-icon { position: relative; z-index: 1; display: inline-block; margin-bottom: 20px; font-size: 1.8rem; filter: drop-shadow(0 4px 6px rgba(0,0,0,0.05)); }
    .bento-card strong { position: relative; z-index: 1; display: block; margin-bottom: 8px; color: var(--ink); font-size: clamp(2.2rem, 4vw, 2.8rem); font-weight: 900; line-height: 1; letter-spacing: -0.04em; }
    .bento-card span { position: relative; z-index: 1; display: block; margin-bottom: 14px; color: var(--primary); font-size: 0.95rem; font-weight: 800; letter-spacing: 0.08em; text-transform: uppercase; }
    .bento-card p { position: relative; z-index: 1; margin: 0; color: var(--ink-soft); font-size: 1rem; line-height: 1.6; }
    .source-inline { margin-top: 24px; color: var(--ink-soft); font-size: 0.95rem; text-align: center; }
    .source-inline a { color: var(--primary); font-weight: 800; text-decoration: underline; text-underline-offset: 3px; }

    /* SECTION MÉTHODE - ECOSYSTEM CARDS */
    .grid-features { display: grid; grid-template-columns: repeat(auto-fit, minmax(320px, 1fr)); gap: 32px; margin-top: 0; }
    .card-feature { position: relative; overflow: hidden; padding: 40px 32px; border: 1px solid var(--border); border-radius: 24px; background: var(--bg-surface); transition: transform 0.3s cubic-bezier(0.25, 1, 0.35, 1), box-shadow 0.3s ease, border-color 0.3s ease; will-change: transform, box-shadow; }
    .card-feature::before { content: ''; position: absolute; top: 0; left: 0; width: 100%; height: 4px; background: linear-gradient(90deg, var(--primary), var(--accent)); opacity: 0; transition: opacity 0.3s ease; }
    .card-feature:hover { transform: translateY(-5px); border-color: rgba(37, 99, 235, 0.2); box-shadow: 0 20px 40px -10px rgba(15, 23, 42, 0.08); }
    .card-feature:hover::before { opacity: 1; }
    .card-feature .icon-box { width: 56px; height: 56px; border: 1px solid rgba(37, 99, 235, 0.1); border-radius: 16px; background: rgba(37, 99, 235, 0.06); display: flex; align-items: center; justify-content: center; margin-bottom: 24px; font-size: 1.6rem; transition: transform 0.3s ease, background 0.3s ease; }
    .card-feature:hover .icon-box { transform: scale(1.05) rotate(-3deg); background: rgba(37, 99, 235, 0.1); }
    .card-feature h3 { margin-bottom: 12px; color: var(--ink); font-size: 1.35rem; font-weight: 800; letter-spacing: -0.02em; }
    .card-feature p { margin: 0; color: var(--ink-soft); font-size: 1rem; line-height: 1.6; }

    /* MOCKUPS APP (FIDÈLES AUX IMAGES) */
    .app-mockup { background: var(--app-bg); border-radius: 16px; border: 1px solid var(--app-border); overflow: hidden; box-shadow: 0 25px 50px -12px rgba(0,0,0,0.5); font-family: 'Inter', sans-serif; color: var(--app-text); text-align: left; }
    .app-header { background: rgba(0,0,0,0.2); padding: 12px 20px; border-bottom: 1px solid var(--app-border); display: flex; justify-content: space-between; align-items: center; font-size: 0.8rem; font-weight: 600; letter-spacing: 0.05em; color: var(--app-text-soft); }

    /* SPECIFIC: QCM MOCKUP */
    .qcm-body { padding: 40px; max-width: 800px; margin: 0 auto; }
    .qcm-question { font-size: 1.2rem; font-weight: 600; margin-bottom: 24px; }
    .qcm-options { display: flex; flex-direction: column; gap: 12px; }
    .qcm-opt { display: flex; align-items: center; gap: 16px; background: var(--app-panel); border: 1px solid var(--app-border); padding: 16px 20px; border-radius: 12px; cursor: pointer; transition: 0.2s; font-size: 1.1rem; }
    .qcm-opt:hover:not(.locked) { border-color: var(--app-text-soft); }
    .qcm-letter { width: 28px; height: 28px; border-radius: 50%; background: rgba(255,255,255,0.1); display: flex; justify-content: center; align-items: center; font-size: 0.8rem; font-weight: 700; color: var(--app-text-soft); }

    /* Etats QCM */
    .qcm-opt.is-correct { border-color: var(--app-green); background: var(--app-green-bg); }
    .qcm-opt.is-correct .qcm-letter { background: var(--app-green); color: white; }
    .qcm-opt.is-wrong { border-color: var(--app-red); background: var(--app-red-bg); }
    .qcm-opt.is-wrong .qcm-letter { background: var(--app-red); color: white; }
    .qcm-opt.locked { cursor: default; opacity: 0.7; }
    .qcm-opt.locked.is-correct, .qcm-opt.locked.is-wrong { opacity: 1; }

    .qcm-feedback-box { margin-top: 24px; background: var(--app-panel); border: 1px solid var(--app-red); border-radius: 12px; padding: 24px; display: none; animation: fadeIn 0.3s; }
    .qcm-feedback-box h4 { color: var(--app-red); font-size: 1.1rem; margin-bottom: 16px; }
    .feedback-card { background: var(--app-bg); border: 1px solid var(--app-border); border-radius: 8px; padding: 16px; margin-bottom: 12px; }
    .feedback-card h5 { display: flex; align-items: center; gap: 8px; color: var(--app-green); margin-bottom: 8px; font-size: 0.95rem; }
    .feedback-card h5.calc { color: #f59e0b; }
    .feedback-actions { display: flex; justify-content: flex-end; gap: 12px; margin-top: 20px; }
    .app-btn { background: rgba(255,255,255,0.1); color: white; border-radius: 8px; padding: 10px 16px; font-size: 0.9rem; font-weight: 600; border: 1px solid rgba(255,255,255,0.1); transition: 0.2s; }
    .app-btn.primary { background: linear-gradient(135deg, #3b82f6, #6366f1); border: none; }
    .app-btn:hover { background: rgba(255,255,255,0.2); }

    /* SECTION DÉMOS - MOCKUP APP & LISTE PREMIUM */
    .premium-list { display: flex; flex-direction: column; gap: 24px; margin: 32px 0 0; padding: 0; list-style: none; }
    .premium-list li { display: flex; align-items: flex-start; gap: 16px; }
    .premium-list .list-icon { width: 28px; height: 28px; border-radius: 50%; background: rgba(16, 185, 129, 0.15); color: var(--green); display: flex; align-items: center; justify-content: center; font-weight: 900; font-size: 0.9rem; flex-shrink: 0; margin-top: 2px; box-shadow: 0 0 12px rgba(16, 185, 129, 0.2); }
    .premium-list .list-content { display: flex; flex-direction: column; gap: 4px; }
    .premium-list .list-content strong { color: var(--ink); font-size: 1.05rem; font-weight: 800; letter-spacing: -0.01em; }
    .premium-list .list-content span { color: var(--ink-soft); font-size: 0.95rem; line-height: 1.5; }

    .app-showcase-wrapper { position: relative; perspective: 1000px; z-index: 1; }
    .app-glow { position: absolute; top: 10%; left: 10%; width: 80%; height: 80%; background: linear-gradient(135deg, rgba(79, 70, 229, 0.4), rgba(16, 185, 129, 0.2)); filter: blur(60px); border-radius: 50%; z-index: -1; opacity: 0.8; pointer-events: none; }
    .app-mockup.dark-premium { background: #0b0f19; border: 1px solid rgba(255, 255, 255, 0.1); border-radius: 18px; box-shadow: 0 25px 60px -15px rgba(0, 0, 0, 0.5), inset 0 1px 0 rgba(255, 255, 255, 0.05); }
    .app-header-mac { background: rgba(255, 255, 255, 0.03); border-bottom: 1px solid rgba(255, 255, 255, 0.08); padding: 14px 20px; display: flex; align-items: center; justify-content: space-between; }
    .mac-dots { display: flex; gap: 8px; width: 96px; }
    .mac-dots span { width: 10px; height: 10px; border-radius: 50%; }
    .dot-red { background: #ff5f56; }
    .dot-yellow { background: #ffbd2e; }
    .dot-green { background: #27c93f; }
    .header-progress { flex-grow: 1; display: flex; justify-content: center; }
    .progress-track { width: 120px; height: 4px; background: rgba(255, 255, 255, 0.1); border-radius: 4px; overflow: hidden; }
    .progress-fill { width: 15%; height: 100%; background: linear-gradient(90deg, #3b82f6, #6366f1); border-radius: 4px; }
    .header-step { width: 96px; text-align: right; color: #6b7280; font-size: 0.75rem; font-weight: 700; letter-spacing: 0.08em; white-space: nowrap; }
    .qcm-feedback-box.active-demo { display: block; box-shadow: inset 0 0 20px rgba(255, 255, 255, 0.02); }
    .qcm-feedback-box.active-demo.is-correct-feedback { border-color: rgba(16, 185, 129, 0.5); background: rgba(16, 185, 129, 0.04); }
    .qcm-feedback-box.active-demo.is-wrong-feedback { border-color: rgba(244, 63, 94, 0.5); background: rgba(244, 63, 94, 0.04); }
    .qcm-feedback-box.active-demo.is-correct-feedback h4 { color: #10b981; }
    .qcm-feedback-box.active-demo.is-wrong-feedback h4 { color: #f43f5e; }
    .qcm-feedback-box .feedback-card { background: rgba(15, 23, 42, 0.6); border: 1px solid rgba(255, 255, 255, 0.05); backdrop-filter: blur(8px); -webkit-backdrop-filter: blur(8px); }
    .qcm-feedback-box .feedback-card p { color: #9ca3af; }
    .qcm-feedback-box .calc-math { font-size: 1.15rem; color: #f3f4f6; padding: 8px 0; }

    /* SPECIFIC: EXERCISE MOCKUP (Pixel Perfect) */
    .exo-layout { display: grid; grid-template-columns: 1fr 1fr; align-items: stretch; background: #0b0f19; font-family: 'Inter', sans-serif; }
    .exo-left { padding: 40px; border-right: 1px solid rgba(255,255,255,0.08); display: flex; flex-direction: column; gap: 32px; }
    .exo-right { background: #111524; display: flex; flex-direction: column; }

    .exo-question { display: flex; justify-content: space-between; align-items: flex-start; gap: 20px; padding-bottom: 24px; border-bottom: 1px solid rgba(255,255,255,0.05); }
    .exo-question-text { font-size: 1.05rem; color: #e5e7eb; line-height: 1.6; }

    .exo-tools { display: flex; gap: 8px; flex-shrink: 0; }
    .exo-tool-btn { width: 42px; height: 42px; border-radius: 8px; background: transparent; border: 1px solid rgba(255,255,255,0.1); color: #9ca3af; display: flex; align-items: center; justify-content: center; font-weight: 700; transition: all 0.2s; font-size: 1.1rem; }
    .exo-tool-btn:hover { background: rgba(255,255,255,0.05); border-color: rgba(255,255,255,0.2); }
    .exo-tool-btn.active { border-color: rgba(255,255,255,0.2); background: rgba(255,255,255,0.05); }
    .exo-tool-btn.active.btn-bulb { color: #facc15; }
    .exo-tool-btn.active.btn-ia { color: #a855f7; }
    .exo-tool-btn.active.btn-corr { color: #10b981; }

    /* Right Panels Base */
    .exo-panel { padding: 32px; display: none; height: 100%; flex-direction: column; animation: fadeIn 0.3s ease-out; }
    .exo-panel.active { display: flex; }
    .panel-header { display: flex; justify-content: space-between; align-items: center; margin-bottom: 24px; }
    .panel-close { color: #6b7280; font-size: 1.2rem; background: rgba(255,255,255,0.05); width: 32px; height: 32px; border-radius: 50%; display: flex; align-items: center; justify-content: center; transition: 0.2s; }
    .panel-close:hover { background: rgba(255,255,255,0.1); color: white; }

    /* Indice Panel & Interactive Sub-tabs (Pixel Perfect) */
    .panel-indice .panel-title { color: #facc15; font-size: 0.9rem; font-weight: 800; letter-spacing: 0.05em; text-transform: uppercase; }

    .indice-pills { display: flex; flex-wrap: wrap; gap: 10px; margin-bottom: 24px; }
    .indice-pill { padding: 8px 16px; border-radius: 99px; font-size: 0.8rem; font-weight: 700; background: rgba(255,255,255,0.03); border: 1px solid rgba(255,255,255,0.05); color: #9ca3af; text-transform: uppercase; letter-spacing: 0.05em; transition: 0.2s; }
    .indice-pill:hover { background: rgba(255,255,255,0.08); }

    /* Active states for each pill */
    .indice-pill.active-def { background: #3b82f6; border-color: #3b82f6; color: white; }
    .indice-pill.active-prop { background: #6d28d9; border-color: #6d28d9; color: white; }
    .indice-pill.active-meth { background: #064e3b; border-color: #10b981; color: #10b981; }
    .indice-pill.active-piege { background: #be123c; border-color: #be123c; color: white; }

    /* Content boxes for each tab */
    .sub-panel { display: none; border-radius: 12px; padding: 24px; animation: fadeIn 0.2s ease-out; }
    .sub-panel.active { display: block; }

    .sub-def { background: rgba(59, 130, 246, 0.08); border: 1px solid rgba(59, 130, 246, 0.2); }
    .sub-def h4 { color: #60a5fa; margin-bottom: 20px; font-size: 1.1rem; }

    .sub-prop { background: rgba(124, 58, 237, 0.08); border: 1px solid rgba(124, 58, 237, 0.2); }
    .sub-prop h4 { color: #a78bfa; margin-bottom: 20px; font-size: 1.1rem; }

    .sub-meth { background: rgba(16, 185, 129, 0.05); border: 1px solid rgba(16, 185, 129, 0.2); }
    .sub-meth h4 { color: #10b981; margin-bottom: 20px; font-size: 1.1rem; }

    .sub-piege { background: rgba(225, 29, 72, 0.08); border: 1px solid rgba(225, 29, 72, 0.2); }
    .sub-piege h4 { color: #fb7185; margin-bottom: 20px; font-size: 1.1rem; }

    /* Common list styles inside sub-panels */
    .step-list { display: flex; flex-direction: column; gap: 16px; }
    .step-list li { display: flex; gap: 16px; font-size: 0.95rem; color: #e5e7eb; line-height: 1.5; }
    .step-list .num { width: 28px; height: 28px; flex-shrink: 0; background: rgba(16, 185, 129, 0.15); border-radius: 50%; display: flex; align-items: center; justify-content: center; font-size: 0.85rem; font-weight: 700; color: #10b981; }

    /* IA Panel */
    .ia-top-btn { align-self: flex-end; border: 1px solid rgba(16, 185, 129, 0.3); color: #e5e7eb; background: rgba(255,255,255,0.03); border-radius: 99px; padding: 8px 20px; font-size: 0.85rem; font-weight: 600; margin-bottom: 24px; transition: 0.2s; }
    .ia-top-btn:hover { background: rgba(16, 185, 129, 0.1); }
    .chat-area { display: flex; flex-direction: column; gap: 16px; margin-bottom: 24px; }
    .chat-msg { color: #d1d5db; font-size: 0.95rem; line-height: 1.5; }
    .ia-suggestions { margin-top: auto; display: flex; flex-direction: column; gap: 16px; }
    .sugg-item { font-size: 0.95rem; color: #d1d5db; line-height: 1.5; }
    .sugg-item span.red { color: #f43f5e; font-weight: 700; }
    .sugg-item span.blue { color: #3b82f6; font-weight: 700; }
    .sugg-item span.purple { color: #a855f7; font-weight: 700; }
    .sugg-actions { display: flex; gap: 12px; margin-top: 8px; }
    .sugg-btn { padding: 8px 24px; border-radius: 99px; border: 1px solid rgba(255,255,255,0.1); background: rgba(255,255,255,0.03); color: #e5e7eb; font-weight: 700; transition: 0.2s; }
    .sugg-btn:hover { background: rgba(255,255,255,0.1); }
    .chat-input { display: flex; align-items: center; background: rgba(255,255,255,0.03); border: 1px solid rgba(255,255,255,0.1); border-radius: 12px; padding: 8px 8px 8px 16px; margin-top: 24px; }
    .chat-input input { flex-grow: 1; background: transparent; border: none; color: white; outline: none; font-family: inherit; font-size: 0.95rem; }
    .chat-input input::placeholder { color: #6b7280; }
    .chat-input button { background: rgba(255,255,255,0.1); color: white; padding: 8px 20px; border-radius: 8px; font-weight: 700; font-size: 0.9rem; transition: 0.2s; }
    .chat-input button:hover { background: rgba(255,255,255,0.2); }

    /* AMÉLIORATION DES COMPOSANTS MOCKUP (Étape 2) */
    .exo-tool-btn.active { background: rgba(255, 255, 255, 0.08); box-shadow: inset 0 0 0 1px currentColor, 0 4px 12px rgba(0, 0, 0, 0.25); transform: translateY(-1px); }
    .chat-input.premium-prompt { background: rgba(255, 255, 255, 0.04); border: 1px solid rgba(255, 255, 255, 0.1); box-shadow: 0 4px 16px rgba(0, 0, 0, 0.2); border-radius: 16px; padding: 8px 8px 8px 18px; margin-top: 24px; transition: border-color 0.3s ease, box-shadow 0.3s ease, background 0.3s ease; }
    .chat-input.premium-prompt:hover { background: rgba(255, 255, 255, 0.06); }
    .chat-input.premium-prompt:focus-within { background: rgba(255, 255, 255, 0.08); border-color: rgba(168, 85, 247, 0.5); box-shadow: 0 0 0 3px rgba(168, 85, 247, 0.15), 0 8px 20px rgba(0, 0, 0, 0.3); }
    .chat-input.premium-prompt input { font-size: 0.95rem; color: #f3f4f6; }
    .chat-input.premium-prompt input::placeholder { color: #6b7280; }
    .chat-input.premium-prompt button { background: linear-gradient(135deg, #a855f7, #6366f1); border-radius: 10px; padding: 8px 20px; font-weight: 700; color: #ffffff; transition: transform 0.2s ease, box-shadow 0.2s ease; }
    .chat-input.premium-prompt button:hover { transform: translateY(-1px); box-shadow: 0 4px 12px rgba(168, 85, 247, 0.4); }
    .chat-input.premium-prompt button:active { transform: translateY(1px); }
    .exo-demo-title { flex-grow: 1; text-align: center; color: #9ca3af; font-size: 0.75rem; font-weight: 700; letter-spacing: 0.08em; }
    .exo-demo-spacer { width: 96px; flex-shrink: 0; }

    /* Correction Panel */
    .panel-correction .panel-title { color: #10b981; font-size: 0.9rem; font-weight: 800; letter-spacing: 0.05em; text-transform: uppercase; }
    .corr-step { border-left: 2px solid rgba(16, 185, 129, 0.5); padding-left: 24px; margin-bottom: 32px; position: relative; }
    .corr-step::before { content: ''; position: absolute; left: -7px; top: 0; width: 12px; height: 12px; border-radius: 50%; background: #0b0f19; border: 2px solid #10b981; }
    .corr-step h5 { color: #10b981; font-size: 0.85rem; text-transform: uppercase; letter-spacing: 0.05em; margin-bottom: 16px; }
    .corr-box { background: rgba(255,255,255,0.02); border: 1px solid rgba(255,255,255,0.05); border-radius: 12px; padding: 24px; display: flex; justify-content: center; align-items: center; color: #e5e7eb; }

    /* SPLIT SECTION */
    .split { display: grid; grid-template-columns: 1fr 1fr; gap: 64px; align-items: center; }
    .split-reverse { direction: rtl; }
    .split-reverse > * { direction: ltr; }
    .demo-live-actions { display: flex; flex-direction: column; align-items: center; gap: 18px; margin: 52px auto 0; text-align: center; }
    .demo-live-actions--subjects { margin-top: 44px; }
    .demo-live-actions__label { margin: 0; color: var(--ink); font-size: 1.05rem; font-weight: 800; letter-spacing: -0.01em; }
    .demo-live-actions__row { display: flex; justify-content: center; gap: 14px; flex-wrap: wrap; }
    .demo-live-actions__row .btn { min-width: 150px; }

    /* SECTION TARIFS - PREMIUM PRICING CARDS */
    .pricing-assurance { display: flex; justify-content: center; gap: 12px; flex-wrap: wrap; margin: 24px auto 0; }
    .pricing-assurance span { display: inline-flex; align-items: center; gap: 8px; padding: 10px 14px; border: 1px solid rgba(16, 185, 129, 0.2); border-radius: 999px; background: rgba(16, 185, 129, 0.08); color: #047857; font-size: 0.92rem; font-weight: 800; }
    .pricing-assurance span::before { content: '✓'; display: grid; place-items: center; width: 18px; height: 18px; border-radius: 999px; background: #10b981; color: #ffffff; font-size: 0.75rem; font-weight: 900; flex-shrink: 0; }
    .pricing-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(320px, 1fr)); gap: 32px; max-width: 1120px; margin: 0 auto; align-items: stretch; }
    .card-price { position: relative; display: flex; flex-direction: column; padding: 48px 36px; border: 1px solid var(--border); border-radius: 32px; background: var(--bg-surface); box-shadow: 0 4px 20px rgba(15, 23, 42, 0.03); transition: transform 0.4s cubic-bezier(0.25, 1, 0.35, 1), box-shadow 0.4s ease, border-color 0.4s ease; }
    .card-price:hover { transform: translateY(-8px); border-color: rgba(37, 99, 235, 0.2); box-shadow: 0 24px 48px -12px rgba(15, 23, 42, 0.1); }
    .card-price.featured { z-index: 2; border: 2px solid var(--primary); background: linear-gradient(180deg, #ffffff 0%, #f8fafc 100%); box-shadow: 0 24px 48px rgba(37, 99, 235, 0.15); transform: scale(1.04); }
    .card-price.featured:hover { transform: scale(1.04) translateY(-8px); box-shadow: 0 32px 64px -12px rgba(37, 99, 235, 0.25); }
    .featured-badge { position: absolute; top: -16px; left: 50%; transform: translateX(-50%); padding: 8px 24px; border-radius: 99px; background: linear-gradient(135deg, var(--primary), var(--accent)); color: white; font-size: 0.85rem; font-weight: 800; letter-spacing: 0.05em; text-transform: uppercase; white-space: nowrap; box-shadow: 0 8px 20px rgba(37, 99, 235, 0.3); }
    .plan-name { margin-bottom: 16px; color: var(--ink-soft); font-size: 1.25rem; font-weight: 800; letter-spacing: 0.05em; text-transform: uppercase; }
    .card-price.featured .plan-name { background: linear-gradient(135deg, var(--primary), var(--accent)); -webkit-background-clip: text; background-clip: text; -webkit-text-fill-color: transparent; }
    .price-val { margin-bottom: 16px; color: var(--ink); font-size: 3.8rem; font-weight: 900; line-height: 1; letter-spacing: -0.03em; }
    .price-val span { display: inline-block; max-width: 9rem; margin-left: 8px; color: var(--ink-faint); font-size: 1.02rem; font-weight: 700; line-height: 1.18; letter-spacing: 0; vertical-align: baseline; }
    .plan-desc { margin-bottom: 32px; padding-bottom: 24px; border-bottom: 1px solid var(--border); color: var(--ink-soft); font-size: 0.95rem; line-height: 1.5; }
    .plan-features { display: flex; flex-direction: column; gap: 16px; flex-grow: 1; margin: 0 0 40px; padding: 0; list-style: none; }
    .plan-features li { display: flex; align-items: flex-start; gap: 12px; color: var(--ink-soft); font-size: 0.95rem; line-height: 1.4; text-align: left; }
    .plan-features li strong { color: var(--ink); font-weight: 700; }
    .plan-features li .text-primary { color: var(--primary); }
    .plan-features li::before { content: '✓'; display: flex; align-items: center; justify-content: center; width: 22px; height: 22px; margin-top: 1px; border-radius: 50%; background: rgba(16, 185, 129, 0.15); color: var(--green); font-size: 0.8rem; font-weight: 900; flex-shrink: 0; }
    .card-price.featured .plan-features li::before { background: linear-gradient(135deg, var(--primary), var(--accent)); color: white; box-shadow: 0 4px 10px rgba(37, 99, 235, 0.25); }
    .plan-btn { width: 100%; height: 56px; font-size: 1.05rem; }
    .glow-btn { position: relative; z-index: 1; overflow: visible; }
    .glow-btn::after { content: ''; position: absolute; inset: 0; z-index: -1; border-radius: 99px; background: linear-gradient(135deg, var(--primary), var(--accent)); opacity: 0; filter: blur(14px); transition: opacity 0.3s ease, transform 0.3s ease; }
    .glow-btn:hover::after { opacity: 0.6; transform: translateY(4px) scale(1.05); }

    /* SECTION FAQ - SPLIT LAYOUT & PREMIUM ACCORDION */
    .faq-split { display: grid; grid-template-columns: 1fr 1.5fr; gap: 64px; align-items: flex-start; }
    .faq-header { position: sticky; top: 100px; }
    .faq-accordion { display: flex; flex-direction: column; border-top: 1px solid var(--border); }
    .faq-item { border-bottom: 1px solid var(--border); transition: background-color 0.3s ease; }
    .faq-item:hover { background-color: rgba(248, 250, 252, 0.5); }
    .faq-item summary { cursor: pointer; padding: 32px 0; color: var(--ink); font-size: 1.15rem; font-weight: 700; line-height: 1.4; list-style: none; display: flex; justify-content: space-between; align-items: center; gap: 24px; }
    .faq-item summary::-webkit-details-marker { display: none; }
    .faq-item summary::after { content: ''; flex-shrink: 0; width: 24px; height: 24px; background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' fill='none' viewBox='0 0 24 24' stroke='%232563eb' stroke-width='2'%3E%3Cpath stroke-linecap='round' stroke-linejoin='round' d='M12 4v16m8-8H4'/%3E%3C/svg%3E"); background-size: cover; transition: transform 0.3s ease; }
    .faq-item[open] summary::after { transform: rotate(45deg); background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' fill='none' viewBox='0 0 24 24' stroke='%23ef4444' stroke-width='2'%3E%3Cpath stroke-linecap='round' stroke-linejoin='round' d='M6 18L18 6M6 6l12 12'/%3E%3C/svg%3E"); }
    .faq-answer { padding-right: 40px; padding-bottom: 32px; color: var(--ink-soft); font-size: 1rem; line-height: 1.7; animation: fadeInDown 0.3s ease-out; }
    .faq-answer strong { color: var(--ink); font-weight: 700; }

    /* SECTION CTA FINAL - DARK PREMIUM BANNER */
    .cta-banner.premium-cta { position: relative; overflow: hidden; padding: 80px 48px; border: 1px solid rgba(255, 255, 255, 0.1); border-radius: 40px; background: #0b0f19; box-shadow: 0 32px 64px -16px rgba(15, 23, 42, 0.4); text-align: center; color: white; z-index: 1; }
    .cta-bg-grid { position: absolute; inset: 0; z-index: -2; background-image: linear-gradient(rgba(255, 255, 255, 0.04) 1px, transparent 1px), linear-gradient(90deg, rgba(255, 255, 255, 0.04) 1px, transparent 1px); background-size: 32px 32px; mask-image: radial-gradient(circle at center, black 40%, transparent 80%); -webkit-mask-image: radial-gradient(circle at center, black 40%, transparent 80%); }
    .premium-cta .glow { position: absolute; border-radius: 50%; filter: blur(70px); z-index: -1; pointer-events: none; }
    .premium-cta .glow-1 { width: 350px; height: 350px; left: -100px; bottom: -150px; background: rgba(79, 70, 229, 0.45); }
    .premium-cta .glow-2 { width: 300px; height: 300px; right: -80px; top: -100px; background: rgba(16, 185, 129, 0.3); }
    .premium-cta .glow-3 { width: 200px; height: 200px; left: 50%; top: 50%; transform: translate(-50%, -50%); background: rgba(14, 165, 233, 0.2); }
    .cta-content { position: relative; z-index: 2; max-width: 680px; margin: 0 auto; }
    .badge-dark { background: rgba(255, 255, 255, 0.08); border: 1px solid rgba(255, 255, 255, 0.15); color: #f3f4f6; box-shadow: none; }
    .badge-dark::before { background: #10b981; box-shadow: 0 0 12px rgba(16, 185, 129, 0.8); }
    .text-gradient-light { background: linear-gradient(135deg, #60a5fa, #a78bfa); -webkit-background-clip: text; background-clip: text; -webkit-text-fill-color: transparent; }
    .premium-cta h2 { color: white; margin-bottom: 20px; }
    .premium-cta .lead { margin: 0 auto 40px; color: #9ca3af; font-size: 1.15rem; line-height: 1.6; max-width: 50ch; }
    .cta-actions { display: flex; justify-content: center; }
    .btn-white { height: 60px; padding: 0 40px; border: none; background: #ffffff; color: #0f172a; font-size: 1.1rem; font-weight: 800; }
    .glow-btn-white { position: relative; z-index: 1; }
    .glow-btn-white::after { content: ''; position: absolute; inset: 0; z-index: -1; border-radius: 99px; background: #ffffff; opacity: 0; filter: blur(14px); transition: opacity 0.3s ease, transform 0.3s ease; }
    .glow-btn-white:hover { transform: translateY(-2px); }
    .glow-btn-white:hover::after { opacity: 0.4; transform: scale(1.05) translateY(4px); }
    .cta-micro { margin-top: 20px; color: #6b7280; font-size: 0.85rem; font-weight: 600; }

    .footer { padding: 28px 0; background: #ffffff; border-top: 1px solid var(--border); color: var(--ink-soft); font-size: 0.92rem; }
    .footer-inner { display: flex; justify-content: space-between; align-items: center; gap: 18px; flex-wrap: wrap; }
    .footer a { color: var(--primary); font-weight: 800; text-decoration: underline; text-underline-offset: 3px; }

    /* MATH UTILS */
    .math { font-family: 'Times New Roman', serif; font-style: italic; font-size: 1.1em; }
    .frac { display: inline-flex; flex-direction: column; align-items: center; vertical-align: middle; margin: 0 4px; }
    .frac span:first-child { border-bottom: 1px solid currentColor; padding: 0 2px; }

    @keyframes fadeInDown { from { opacity: 0; transform: translateY(-10px); } to { opacity: 1; transform: translateY(0); } }
    @keyframes fadeIn { from { opacity: 0; transform: translateY(5px); } to { opacity: 1; transform: translateY(0); } }

    /* SCROLL REVEAL ANIMATIONS */
    .reveal {
      --reveal-delay: 0ms;
      --reveal-distance: 64px;
      --reveal-duration: 1050ms;
      --reveal-ease: cubic-bezier(0.16, 1, 0.3, 1);
      opacity: 1;
      transform: none;
      will-change: opacity, transform;
    }
    .reveal-ready .reveal {
      opacity: 0;
      transform: translate3d(0, var(--reveal-distance), 0) scale(0.985);
      transition: opacity var(--reveal-duration) var(--reveal-ease), transform var(--reveal-duration) var(--reveal-ease);
      transition-delay: var(--reveal-delay);
    }
    .reveal-ready .reveal.is-visible {
      opacity: 1;
      transform: translate3d(0, 0, 0) scale(1);
    }
    .reveal-d1 { --reveal-delay: 140ms; }
    .reveal-d2 { --reveal-delay: 280ms; }
    .reveal-d3 { --reveal-delay: 420ms; }
    .reveal-d4 { --reveal-delay: 560ms; }

    @media (max-width: 992px) {
      .section { padding: 88px 0; }
      .section-head { margin-bottom: 48px; }
      .hero-grid { grid-template-columns: 1fr; gap: 38px; }
      .hero-media.stack-container { min-height: 500px; margin-top: 24px; }
      .stack-card { width: min(580px, 90%); }
      .stack-card.is-next, .stack-card.pos-2 { transform: translate3d(20%, 0%, -60px) scale(0.85) rotate(6deg); }
      .stack-card.is-prev, .stack-card.pos-3 { transform: translate3d(-20%, 0%, -60px) scale(0.85) rotate(-6deg); }
      .official-bento { grid-template-columns: repeat(2, 1fr); gap: 20px; }
      .bento-card.top-row, .bento-card.bottom-row { grid-column: span 1; }
      .bento-card.top-row:nth-child(3) { grid-column: span 2; }
      .split { grid-template-columns: 1fr; gap: 40px; }
      .exo-layout { grid-template-columns: 1fr; }
      .exo-left { border-right: none; border-bottom: 1px solid var(--app-border); }
      .pricing-grid { grid-template-columns: 1fr; max-width: 500px; }
      .card-price.featured { z-index: 1; transform: scale(1); }
      .card-price.featured:hover { transform: translateY(-4px); }
      .faq-split { grid-template-columns: 1fr; gap: 32px; }
      .faq-header { position: static; }
      .faq-item summary { padding: 24px 0; font-size: 1.05rem; }
      .faq-answer { padding-right: 0; }
      .nav-links { display: none; }
    }

    @media (max-width: 640px) {
      .section { padding: 64px 0; }
      .section-head { margin-bottom: 40px; }
      .hero { padding: 104px 0 64px; }
      .official-bento { grid-template-columns: 1fr; gap: 16px; margin-top: 0; }
      .bento-card.top-row, .bento-card.bottom-row, .bento-card.top-row:nth-child(3) { grid-column: span 1; }
      .bento-card { padding: 28px 24px; }
      .btn { width: 100%; }
      .nav-shell { padding: 10px 14px; }
      .nav-login { display: none; }
      .nav-actions .btn-primary { width: auto; padding: 0 20px; }
      .hero-media.stack-container { min-height: clamp(380px, 85vw, 500px); margin-top: 16px; }
      .stack-card { width: 95%; max-width: none; transform-origin: 50% 80%; }
      .stack-card.is-active, .stack-card.pos-1 { transform: translate3d(0, -5%, 50px) scale(1) rotate(0deg); }
      .stack-card.is-next, .stack-card.pos-2 { transform: translate3d(12%, 2%, -50px) scale(0.85) rotate(5deg); opacity: 0.5; }
      .stack-card.is-prev, .stack-card.pos-3 { transform: translate3d(-12%, 2%, -50px) scale(0.85) rotate(-5deg); opacity: 0.5; }
      .stack-card .browser-label { min-height: 48px; font-size: 0.78rem; line-height: 1.35; padding: 8px 12px; }
      .stack-dots { bottom: 0; }
      .grid-features { grid-template-columns: 1fr; gap: 20px; margin-top: 0; }
      .card-feature { padding: 32px 24px; }
      .premium-list { gap: 20px; margin-top: 28px; }
      .demo-live-actions { margin-top: 40px; }
      .demo-live-actions__row { width: 100%; }
      .demo-live-actions__row .btn { min-width: 0; }
      .pricing-assurance { flex-direction: column; align-items: stretch; max-width: 320px; }
      .pricing-assurance span { justify-content: center; }
      .qcm-body, .exo-left, .exo-panel { padding: 22px; }
      .cta-banner.premium-cta { padding: 48px 24px; border-radius: 32px; }
      .premium-cta h2 { font-size: 1.8rem; }
      .premium-cta .lead { font-size: 1rem; }
      .btn-white { width: 100%; }
      .footer-inner { align-items: flex-start; }
      .reveal {
        --reveal-distance: 44px;
        --reveal-duration: 900ms;
      }
      .reveal-d1 { --reveal-delay: 90ms; }
      .reveal-d2 { --reveal-delay: 180ms; }
      .reveal-d3 { --reveal-delay: 270ms; }
      .reveal-d4 { --reveal-delay: 360ms; }
    }

    @media (prefers-reduced-motion: reduce) {
      .stack-card { transition: none; }
      .stack-dot::before { transition: none; }
      .reveal,
      .reveal-ready .reveal {
        opacity: 1;
        transform: none;
        transition: none;
      }
    }

    /* RESPONSIVE HARDENING PATCH */
    html,
    body {
      overflow-x: clip;
    }

    @media (min-width: 641px) and (max-width: 992px) {
      .shell {
        padding: 0 32px;
      }

      .app-mockup,
      .exo-layout {
        width: 100%;
        max-width: 100%;
        min-width: 0;
      }
    }

    @media (max-width: 640px) {
      .hero-media.stack-container {
        min-height: clamp(380px, 78vw, 500px);
        perspective: 800px;
      }

      .stack-card {
        width: 100%;
        border-radius: 16px;
      }

      .stack-card.is-active,
      .stack-card.pos-1 { transform: translate3d(0, -5%, 30px) scale(1) rotate(0deg); }

      .stack-card.is-next,
      .stack-card.pos-2 { transform: translate3d(8%, 2%, -30px) scale(0.9) rotate(3deg); }

      .stack-card.is-prev,
      .stack-card.pos-3 { transform: translate3d(-8%, 2%, -30px) scale(0.9) rotate(-3deg); }

      .qcm-body,
      .exo-left,
      .exo-right,
      .qcm-feedback-box,
      .app-mockup {
        min-width: 0;
      }

      .chat-msg,
      .sugg-item,
      .panel-title,
      .feedback-card p {
        overflow-wrap: break-word;
      }

      .corr-box,
      div.math,
      .calc-math {
        max-width: 100%;
        overflow-x: auto;
        padding-bottom: 4px;
        scrollbar-width: thin;
      }

      .corr-box .math,
      div.math,
      .calc-math .math {
        white-space: nowrap;
      }

      .corr-box::-webkit-scrollbar,
      div.math::-webkit-scrollbar,
      .calc-math::-webkit-scrollbar {
        height: 4px;
      }

      .corr-box::-webkit-scrollbar-thumb,
      div.math::-webkit-scrollbar-thumb,
      .calc-math::-webkit-scrollbar-thumb {
        background: rgba(0, 0, 0, 0.1);
        border-radius: 4px;
      }

      .app-header-mac { padding: 12px 14px; }
      .mac-dots { width: 45px; }
      .header-step { width: auto; font-size: 0.65rem; }
      .exo-demo-spacer { width: 45px; }
      .exo-demo-title {
        min-width: 0;
        overflow: hidden;
        text-overflow: ellipsis;
        white-space: nowrap;
        font-size: 0.68rem;
      }
      .qcm-opt { padding: 12px; gap: 12px; font-size: 0.95rem; }
      .bento-card { padding: 24px 20px; border-radius: 20px; }
      .card-price { padding: 32px 20px; border-radius: 24px; }

      .chat-input.premium-prompt {
        flex-direction: column;
        gap: 12px;
        padding: 12px;
      }

      .chat-input.premium-prompt input {
        width: 100%;
        text-align: center;
      }

      .chat-input.premium-prompt button {
        width: 100%;
      }
    }

    @media (max-width: 380px) {
      .hero-copy h1,
      .section-head h2 {
        font-size: clamp(1.8rem, 8vw, 2.2rem);
        letter-spacing: -0.02em;
      }

      .btn {
        padding: 0 16px;
        font-size: 0.95rem;
      }

      .price-val {
        font-size: 2.8rem;
      }

      .bento-card strong {
        font-size: 1.6rem;
      }

      .brand-copy strong {
        font-size: 1rem;
      }
    }