:root {
      --text: #1f2937;
      --sub: #4b5563;
      --border: #e5e7eb;
      --bg: #ffffff;
      --accent: #111827;
      --btn-bg: #f3f4f6;
      --btn-active-bg: #111827;
      --btn-active-text: #ffffff;
    }

    * {
      box-sizing: border-box;
    }

    body {
      margin: 0;
      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Hiragino Sans", "Hiragino Kaku Gothic ProN", "Yu Gothic", "Meiryo", sans-serif;
      color: var(--text);
      background: #f9fafb;
      line-height: 1.8;
    }

    .container {
      max-width: 920px;
      margin: 0 auto;
      padding: 40px 20px 80px;
    }

    .lang-switch {
      display: flex;
      justify-content: flex-end;
      gap: 4px;
      margin-bottom: 16px;
    }

    .lang-switch button {
      border: 1px solid var(--border);
      background: var(--btn-bg);
      color: var(--text);
      padding: 6px 14px;
      font-size: 0.85rem;
      border-radius: 8px;
      cursor: pointer;
      transition: all 0.15s ease;
      font-family: inherit;
    }

    .lang-switch button:hover {
      background: #e5e7eb;
    }

    .lang-switch button.active {
      background: var(--btn-active-bg);
      color: var(--btn-active-text);
      border-color: var(--btn-active-bg);
    }

    .card {
      background: var(--bg);
      border: 1px solid var(--border);
      border-radius: 16px;
      padding: 32px 24px;
      box-shadow: 0 4px 16px rgba(0, 0, 0, 0.04);
    }

    h1 {
      margin: 0 0 12px;
      font-size: 2rem;
      line-height: 1.4;
      color: var(--accent);
    }

    .lead {
      margin: 0 0 28px;
      color: var(--sub);
      font-size: 0.98rem;
    }

    h2 {
      margin-top: 32px;
      margin-bottom: 12px;
      font-size: 1.2rem;
      border-left: 4px solid var(--accent);
      padding-left: 12px;
    }

    h3 {
      margin-top: 20px;
      margin-bottom: 8px;
      font-size: 1rem;
    }

    p {
      margin: 0 0 14px;
    }

    ul, ol {
      margin: 0 0 16px 1.2em;
      padding: 0;
    }

    li {
      margin-bottom: 8px;
    }

    .meta {
      margin-top: 36px;
      padding-top: 20px;
      border-top: 1px solid var(--border);
      color: var(--sub);
      font-size: 0.95rem;
    }

    [data-lang-content] {
      display: none;
    }

    [data-lang-content].active {
      display: block;
    }

    @media (max-width: 640px) {
      .container {
        padding: 20px 12px 48px;
      }

      .card {
        padding: 24px 16px;
        border-radius: 12px;
      }

      h1 {
        font-size: 1.6rem;
      }
    }
.security-note {
  font-size: 0.88rem;
  padding: 12px 14px;
  background: #f3f4f6;
  border-radius: 8px;
}