:root {
      --ink: #06131f;
      --paper: #ffffff;
      --line: #dbe3ea;
      --muted: #4b5563;
      --signal: #0b63ce;
      --font-sans: HelveticaNeue, "Helvetica Neue", Helvetica, Arial,
        "游ゴシック体", YuGothic, "游ゴシック Medium", "Yu Gothic Medium",
        "游ゴシック", "Yu Gothic", "ヒラギノ角ゴ ProN W3", "Hiragino Kaku Gothic ProN",
        "ヒラギノ角ゴ Pro W3", "Hiragino Kaku Gothic Pro", "MS ゴシック", "MS Gothic",
        sans-serif;
      --font-mono: "SF Mono", "Fira Code", "Fira Mono", Menlo, Consolas, monospace;
      font-family: var(--font-sans);
      color: var(--ink);
      background: var(--paper);
    }

    * { box-sizing: border-box; }

    html { scroll-behavior: smooth; }

    body {
      margin: 0;
      font-size: 16px;
      line-height: 1.8;
      font-feature-settings: "palt";
      -webkit-font-smoothing: antialiased;
      word-wrap: break-word;
      background: #f8f7f2;
    }

    a { color: inherit; text-decoration: none; }
    img { display: block; max-width: 100%; height: auto; }

    .site-header {
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 18px;
      min-height: 62px;
      padding: 14px clamp(20px, 4vw, 58px) 10px;
      background: #f8f7f2;
      box-shadow: inset 0 -1px 0 rgba(6, 19, 31, 0.08);
    }

    .brand {
      display: inline-flex;
      align-items: center;
      gap: 7px;
    }

    .brand-symbol { width: 40px; }
    .brand-wordmark { width: 96px; }

    main {
      max-width: 820px;
      margin: 0 auto;
      padding: clamp(40px, 7vw, 88px) clamp(20px, 4vw, 40px) clamp(60px, 9vw, 120px);
    }

    .breadcrumb {
      margin-bottom: 18px;
      color: var(--muted);
      font-family: var(--font-mono);
      font-size: 11px;
      font-weight: 780;
      letter-spacing: 0.06em;
    }

    .breadcrumb a {
      text-decoration: underline;
      text-underline-offset: 3px;
    }

    .breadcrumb a:hover,
    .breadcrumb a:focus-visible {
      color: var(--signal);
      outline: none;
    }

    .section-label {
      margin: 0;
      color: var(--signal);
      font-family: var(--font-mono);
      font-size: 12px;
      font-weight: 780;
      letter-spacing: 0.1em;
      text-transform: uppercase;
    }

    h1 {
      margin: 14px 0 18px;
      font-size: clamp(27px, 3.8vw, 40px);
      font-weight: 820;
      line-height: 1.28;
      letter-spacing: 0.02em;
    }

    .hub-lead {
      margin: 0 0 14px;
      font-size: 16.5px;
      line-height: 1.9;
    }

    .hub-note {
      margin: 0 0 44px;
      color: var(--muted);
      font-size: 14px;
      line-height: 1.8;
    }

    h2 {
      margin: 0 0 6px;
      font-size: clamp(19px, 2.3vw, 23px);
      font-weight: 850;
      letter-spacing: 0.015em;
    }

    .section-note {
      margin: 0 0 18px;
      color: var(--muted);
      font-size: 14px;
    }

    section { margin-bottom: clamp(40px, 6vw, 64px); }

    .hub-cards {
      display: grid;
      gap: 12px;
    }

    .hub-card {
      display: grid;
      gap: 6px;
      padding: 22px clamp(18px, 2.4vw, 26px);
      border: 1px solid var(--line);
      background: var(--paper);
      transition: border-color 0.18s ease, transform 0.18s ease, box-shadow 0.18s ease;
    }

    .hub-card:hover,
    .hub-card:focus-visible {
      border-color: var(--signal);
      transform: translateY(-2px);
      box-shadow: 0 12px 28px -20px rgba(6, 19, 31, 0.6);
      outline: none;
    }

    .hub-card-kicker {
      color: var(--signal);
      font-family: var(--font-mono);
      font-size: 11px;
      font-weight: 800;
      letter-spacing: 0.08em;
      text-transform: uppercase;
    }

    .hub-card-title {
      font-size: 17px;
      font-weight: 830;
      line-height: 1.55;
    }

    .hub-card-note {
      color: var(--muted);
      font-size: 13.5px;
      line-height: 1.75;
    }

    .hub-card.primary {
      border-color: var(--ink);
      background: var(--ink);
      color: var(--paper);
    }

    .hub-card.primary .hub-card-kicker { color: rgba(255, 255, 255, 0.66); }
    .hub-card.primary .hub-card-note { color: rgba(255, 255, 255, 0.74); }

    .hub-card.primary:hover,
    .hub-card.primary:focus-visible { border-color: var(--signal); }

    .video-list {
      display: grid;
      grid-template-columns: repeat(3, minmax(0, 1fr));
      gap: 14px;
    }

    .video-card {
      display: grid;
      align-content: start;
      gap: 10px;
      border: 1px solid var(--line);
      background: var(--paper);
      transition: border-color 0.18s ease, transform 0.18s ease;
    }

    .video-card:hover,
    .video-card:focus-visible {
      border-color: var(--signal);
      transform: translateY(-2px);
      outline: none;
    }

    .video-card img {
      width: 100%;
      aspect-ratio: 16 / 9;
      object-fit: cover;
      background: #eef2f5;
    }

    .video-card-body {
      display: grid;
      gap: 6px;
      padding: 0 15px 17px;
    }

    .video-card-title {
      font-size: 14px;
      font-weight: 800;
      line-height: 1.6;
    }

    .video-card-meta {
      color: var(--muted);
      font-family: var(--font-mono);
      font-size: 11px;
      letter-spacing: 0.04em;
    }

    .term-list {
      display: flex;
      flex-wrap: wrap;
      gap: 9px;
      padding: 0;
      margin: 0;
      list-style: none;
    }

    .term-list a {
      display: inline-flex;
      padding: 9px 16px;
      border: 1px solid var(--line);
      background: var(--paper);
      font-size: 13.5px;
      font-weight: 760;
      transition: border-color 0.18s ease, color 0.18s ease;
    }

    .term-list a:hover,
    .term-list a:focus-visible {
      border-color: var(--signal);
      color: var(--signal);
      outline: none;
    }

    .faq-item {
      padding: 20px 0;
      border-top: 1px solid var(--line);
    }

    .faq-item:last-of-type { border-bottom: 1px solid var(--line); }

    .faq-item h3 {
      margin: 0 0 8px;
      font-size: 15.5px;
      font-weight: 830;
      line-height: 1.6;
    }

    .faq-item p {
      margin: 0;
      color: var(--muted);
      font-size: 14.5px;
      line-height: 1.85;
    }

    .connect-strip {
      margin-bottom: 0;
      padding: 26px clamp(18px, 2.6vw, 30px);
      border: 1px solid var(--line);
      background: linear-gradient(180deg, rgba(11, 99, 206, 0.05), rgba(11, 99, 206, 0.015));
    }

    .connect-strip h2 { margin-bottom: 16px; }

    .connect-actions {
      display: flex;
      flex-wrap: wrap;
      gap: 10px;
    }

    .connect-button {
      display: inline-flex;
      align-items: center;
      padding: 10px 18px;
      border: 1px solid var(--line);
      background: var(--paper);
      font-size: 13.5px;
      font-weight: 780;
      transition: border-color 0.18s ease, color 0.18s ease, transform 0.18s ease;
    }

    .connect-button:hover,
    .connect-button:focus-visible {
      border-color: var(--signal);
      color: var(--signal);
      transform: translateY(-1px);
      outline: none;
    }

    .connect-button.primary {
      border-color: var(--signal);
      background: var(--signal);
      color: #fff;
    }

    .connect-button.primary:hover,
    .connect-button.primary:focus-visible {
      color: #fff;
      filter: brightness(1.08);
    }

    .site-footer {
      display: flex;
      flex-wrap: wrap;
      align-items: center;
      justify-content: space-between;
      gap: 10px 16px;
      padding: 18px clamp(20px, 4vw, 58px);
      background: linear-gradient(180deg, #eef2f5 0%, #f8f7f2 62%);
      box-shadow: inset 0 1px 0 rgba(6, 19, 31, 0.08);
      color: var(--muted);
      font-family: var(--font-mono);
      font-size: 11px;
      font-weight: 850;
      letter-spacing: 0.04em;
      text-transform: uppercase;
    }

    .site-footer a:hover,
    .site-footer a:focus-visible {
      color: var(--signal);
      outline: none;
    }

    @media (max-width: 760px) {
      .video-list { grid-template-columns: minmax(0, 1fr); }
    }

    @media (max-width: 420px) {
      .connect-actions { flex-direction: column; align-items: stretch; }
      .connect-button { justify-content: center; }
    }