:root {
      --bg:      #0b1726;
      --bg2:     #0e1e35;
      --bg3:     #132540;
      --primary: #4a90d9;
      --primary2:#6aaff0;
      --text:    #e8eef7;
      --muted:   #8fa8c8;
      --border:  rgba(74, 144, 217, 0.18);
      --radius:  14px;
    }

    * { box-sizing: border-box; margin: 0; padding: 0; }

    body {
      background: var(--bg);
      color: var(--text);
      font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
      line-height: 1.7;
    }

    nav {
      display: flex;
      align-items: center;
      justify-content: space-between;
      padding: 18px 32px;
      border-bottom: 1px solid var(--border);
      background: rgba(11,23,38,0.85);
      backdrop-filter: blur(12px);
      position: sticky;
      top: 0;
      z-index: 100;
    }

    .logo {
      font-size: 1.65rem;
      font-weight: 700;
      color: var(--primary2);
      letter-spacing: -0.5px;
      text-decoration: none;
    }

    .back {
      color: var(--primary2);
      text-decoration: none;
      font-size: 0.9rem;
      font-weight: 600;
    }

    .back:hover { text-decoration: underline; }

    .nav-right { display: flex; align-items: center; gap: 18px; }

    .lang-select { position: relative; }
    .lang-select-btn {
      display: flex;
      align-items: center;
      gap: 6px;
      font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
      font-size: 0.82rem;
      font-weight: 600;
      background: transparent;
      color: var(--muted);
      border: 1px solid var(--border);
      border-radius: 8px;
      padding: 5px 9px;
      cursor: pointer;
      transition: color 0.18s, border-color 0.18s;
    }
    .lang-select-btn:hover, .lang-select-btn[aria-expanded="true"] { color: var(--text); border-color: var(--primary2); }
    .lang-select-caret { flex: none; transition: transform 0.18s; }
    .lang-select-btn[aria-expanded="true"] .lang-select-caret { transform: rotate(180deg); }
    .lang-select-menu {
      position: absolute;
      top: calc(100% + 6px);
      right: 0;
      min-width: 168px;
      max-height: 60vh;
      overflow-y: auto;
      background: var(--bg2);
      border: 1px solid var(--border);
      border-radius: var(--radius);
      padding: 6px;
      margin: 0;
      list-style: none;
      box-shadow: 0 12px 32px -8px rgba(0,0,0,0.5);
      opacity: 0;
      visibility: hidden;
      transform: translateY(-4px);
      transition: opacity 0.16s, transform 0.16s, visibility 0.16s;
      z-index: 200;
    }
    .lang-select.open .lang-select-menu { opacity: 1; visibility: visible; transform: translateY(0); }
    .lang-select-menu a {
      display: block;
      padding: 7px 10px;
      border-radius: 6px;
      font-size: 0.86rem;
      color: var(--muted);
      text-decoration: none;
      transition: background 0.14s, color 0.14s;
    }
    .lang-select-menu a:hover, .lang-select-menu a:focus-visible { background: var(--bg3); color: var(--text); }
    .lang-select-menu li[aria-selected="true"] a { color: var(--primary2); }

    main {
      max-width: 720px;
      margin: 0 auto;
      padding: 60px 24px 80px;
    }

    .meta {
      color: var(--muted);
      font-size: 0.85rem;
      margin-bottom: 40px;
    }

    h1 {
      font-size: clamp(1.6rem, 4vw, 2.2rem);
      font-weight: 800;
      color: #fff;
      letter-spacing: -0.5px;
      margin-bottom: 6px;
    }

    h2 {
      font-size: 1.1rem;
      font-weight: 700;
      color: var(--primary2);
      margin: 36px 0 10px;
    }

    p { color: var(--muted); margin-bottom: 12px; }

    strong { color: var(--text); }

    ul {
      color: var(--muted);
      padding-left: 20px;
      margin-bottom: 12px;
    }

    ul li { margin-bottom: 4px; }

    a { color: var(--primary2); }

    hr {
      border: none;
      border-top: 1px solid var(--border);
      margin: 28px 0;
    }

    footer {
      border-top: 1px solid var(--border);
      text-align: center;
      padding: 24px;
      color: var(--muted);
      font-size: 0.82rem;
    }

    @media (max-width: 600px) {
      nav { padding: 14px 16px; }
    }