:root {
      --bg: #f8fafc;
      --bg-soft: #f1f5f9;
      --panel: rgba(255, 255, 255, 0.8);
      --panel-solid: #ffffff;
      --card: rgba(0, 0, 0, 0.03);
      --card-strong: rgba(0, 0, 0, 0.05);
      --line: rgba(0, 0, 0, 0.06);
      --line-strong: rgba(0, 0, 0, 0.1);
      --text: #0f172a;
      --muted: #475569;
      --subtle: #64748b;
      --primary: #0284c7;
      --primary-strong: #0369a1;
      --secondary: #7c3aed;
      --accent: #ea580c;
      --max: 1180px;
      --radius-xxl: 32px;
      --radius-xl: 24px;
      --radius-lg: 18px;
      --shadow-lg: 0 20px 50px rgba(0, 0, 0, 0.08);
      --shadow-md: 0 10px 30px rgba(0, 0, 0, 0.06);
      --topbar-bg: rgba(255, 255, 255, 0.8);
      --hero-bg: linear-gradient(135deg, #ffffff 0%, #f1f5f9 100%);
      --body-bg: radial-gradient(circle at top left, rgba(2, 132, 199, 0.06), transparent 30%),
                 radial-gradient(circle at top right, rgba(124, 58, 237, 0.05), transparent 28%),
                 #f8fafc;
    }

    body.dark-mode {
      --bg: #0b1220;
      --bg-soft: #111827;
      --panel: rgba(15, 23, 42, 0.74);
      --panel-solid: #0f172a;
      --card: rgba(255, 255, 255, 0.06);
      --card-strong: rgba(255, 255, 255, 0.08);
      --line: rgba(255, 255, 255, 0.12);
      --line-strong: rgba(255, 255, 255, 0.18);
      --text: #e5eefc;
      --muted: #9fb0c9;
      --subtle: #7d8ca5;
      --primary: #55c2ff;
      --primary-strong: #1793d1;
      --secondary: #8b5cf6;
      --accent: #f8b84e;
      --shadow-lg: 0 24px 80px rgba(0, 0, 0, 0.32);
      --shadow-md: 0 16px 44px rgba(0, 0, 0, 0.22);
      --topbar-bg: rgba(11, 18, 32, 0.7);
      --hero-bg: linear-gradient(135deg, rgba(17, 24, 39, 0.92) 0%, rgba(15, 23, 42, 0.86) 100%);
      --body-bg: radial-gradient(circle at top left, rgba(85, 194, 255, 0.18), transparent 30%),
                 radial-gradient(circle at top right, rgba(139, 92, 246, 0.16), transparent 28%),
                 linear-gradient(180deg, #0b1220 0%, #0f172a 45%, #0b1220 100%);
    }

    * { box-sizing: border-box; }
    html { scroll-behavior: smooth; }
    body {
      margin: 0;
      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Noto Sans KR", "Apple SD Gothic Neo", sans-serif;
      color: var(--text);
      background: var(--body-bg);
      line-height: 1.65;
      transition: background 0.3s ease, color 0.3s ease;
    }

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

    .wrap {
      width: min(calc(100% - 32px), var(--max));
      margin: 0 auto;
    }

    .topbar {
      position: sticky;
      top: 0;
      z-index: 40;
      backdrop-filter: blur(20px);
      background: var(--topbar-bg);
      border-bottom: 1px solid var(--line);
    }

    .topbar-inner {
      min-height: 76px;
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 20px;
    }

    .brand {
      display: flex;
      align-items: center;
      gap: 14px;
      font-weight: 800;
      letter-spacing: -0.04em;
    }

    .brand-mark {
      width: 42px;
      height: 42px;
      border-radius: 14px;
      display: grid;
      place-items: center;
      background: linear-gradient(135deg, var(--primary) 0%, var(--secondary) 100%);
      color: white;
      box-shadow: var(--shadow-md);
      font-size: 14px;
    }

    .brand small {
      display: block;
      color: var(--subtle);
      font-size: 12px;
      font-weight: 700;
      letter-spacing: 0.04em;
      margin-top: 2px;
    }

    .nav {
      display: flex;
      flex-wrap: wrap;
      align-items: center;
      gap: 10px;
    }

    .nav a {
      padding: 10px 14px;
      border-radius: 999px;
      font-size: 14px;
      color: var(--muted);
      font-weight: 700;
      transition: 0.2s ease;
    }

    .nav a:hover {
      background: var(--card);
      color: var(--text);
    }

    /* Theme Toggle Button */
    .theme-toggle {
      width: 40px;
      height: 40px;
      border-radius: 12px;
      border: 1px solid var(--line);
      background: var(--card);
      color: var(--text);
      cursor: pointer;
      display: grid;
      place-items: center;
      transition: 0.2s ease;
      margin-left: 8px;
    }

    .theme-toggle:hover {
      background: var(--card-strong);
      transform: scale(1.05);
    }

    .theme-toggle svg {
      width: 20px;
      height: 20px;
    }

    .hero {
      padding: 42px 0 26px;
    }

    .hero-shell {
      position: relative;
      overflow: hidden;
      border-radius: var(--radius-xxl);
      border: 1px solid var(--line);
      background: var(--hero-bg);
      box-shadow: var(--shadow-lg);
    }

    .hero-shell::before,
    .hero-shell::after {
      content: "";
      position: absolute;
      border-radius: 999px;
      filter: blur(12px);
      pointer-events: none;
    }

    .hero-shell::before {
      width: 320px;
      height: 320px;
      top: -120px;
      right: -80px;
      background: rgba(85, 194, 255, 0.16);
    }

    .hero-shell::after {
      width: 280px;
      height: 280px;
      left: -80px;
      bottom: -120px;
      background: rgba(139, 92, 246, 0.16);
    }

    .hero-grid {
      position: relative;
      z-index: 1;
      display: grid;
      grid-template-columns: 1.2fr 0.8fr;
      gap: 28px;
      padding: 38px;
    }

    .eyebrow {
      display: inline-flex;
      align-items: center;
      gap: 10px;
      padding: 10px 16px;
      border-radius: 999px;
      border: 1px solid rgba(85, 194, 255, 0.28);
      background: rgba(85, 194, 255, 0.08);
      color: var(--primary);
      font-size: 13px;
      font-weight: 800;
      letter-spacing: 0.03em;
      margin-bottom: 20px;
    }

    h1 {
      margin: 0;
      font-size: clamp(38px, 6vw, 68px);
      line-height: 1.04;
      letter-spacing: -0.06em;
      color: var(--text);
    }

    .headline {
      margin: 0;
      font-size: clamp(18px, 3vw, 24px);
      color: var(--text);
      opacity: 0.9;
      font-weight: 700;
      letter-spacing: -0.03em;
    }

    .hero-copy {
      margin-top: 18px;
      max-width: 760px;
      font-size: 17px;
      color: var(--muted);
    }

    .impact-row {
      display: grid;
      grid-template-columns: repeat(3, minmax(0, 1fr));
      gap: 14px;
      margin-top: 26px;
    }

    .impact-card {
      padding: 18px;
      border-radius: 20px;
      background: var(--card);
      border: 1px solid var(--line);
    }

    .impact-card strong {
      display: block;
      margin-bottom: 6px;
      font-size: 28px;
      line-height: 1;
      letter-spacing: -0.05em;
      color: var(--text);
    }

    .impact-card span {
      display: block;
      color: var(--muted);
      font-size: 14px;
      font-weight: 700;
    }

    .hero-tags {
      display: flex;
      flex-wrap: wrap;
      gap: 10px;
      margin-top: 24px;
    }

    .tag {
      padding: 10px 14px;
      border-radius: 999px;
      background: var(--card);
      border: 1px solid var(--line);
      color: var(--text);
      font-size: 14px;
      font-weight: 700;
    }

    .cta-row {
      display: flex;
      flex-wrap: wrap;
      gap: 12px;
      margin-top: 28px;
    }

    .btn {
      min-height: 50px;
      padding: 0 18px;
      border-radius: 14px;
      display: inline-flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      font-size: 15px;
      font-weight: 800;
      transition: 0.2s ease;
      border: 1px solid transparent;
    }

    .btn-primary {
      background: linear-gradient(135deg, var(--primary) 0%, var(--primary-strong) 100%);
      color: white;
      box-shadow: 0 14px 30px rgba(2, 132, 199, 0.2);
    }

    .btn-primary:hover { transform: translateY(-1px); }

    .btn-secondary {
      background: var(--card);
      border-color: var(--line);
      color: var(--text);
    }

    .btn-secondary:hover {
      background: var(--card-strong);
    }

    .hero-side {
      display: grid;
      gap: 16px;
      align-content: start;
    }

    .profile-card,
    .side-card,
    .section-card,
    .timeline-item,
    .project-card,
    .skill-card,
    .edu-card {
      background: var(--card);
      border: 1px solid var(--line);
      border-radius: var(--radius-xl);
      box-shadow: var(--shadow-md);
      transition: transform 0.2s ease, background 0.3s ease;
    }

    .profile-card {
      padding: 18px;
    }

    .profile-meta {
      margin-top: 16px;
      display: grid;
      gap: 12px;
    }

    .meta-item strong {
      display: block;
      color: var(--subtle);
      font-size: 12px;
      font-weight: 800;
      letter-spacing: 0.04em;
      text-transform: uppercase;
      margin-bottom: 4px;
    }

    .meta-item span,
    .meta-item a {
      color: var(--text);
      font-size: 15px;
      font-weight: 700;
      word-break: break-word;
    }

    .side-card {
      padding: 18px;
    }

    .side-title {
      margin: 0 0 12px;
      color: var(--text);
      font-size: 15px;
      font-weight: 800;
      letter-spacing: -0.02em;
    }

    .side-list {
      margin: 0;
      padding-left: 18px;
      color: var(--muted);
    }

    .side-list li + li { margin-top: 8px; }

    .section {
      padding: 18px 0;
    }

    .section-head {
      display: flex;
      align-items: end;
      justify-content: space-between;
      gap: 16px;
      margin-bottom: 18px;
    }

    .section-kicker {
      display: inline-block;
      margin-bottom: 10px;
      color: var(--primary);
      font-size: 12px;
      font-weight: 800;
      letter-spacing: 0.1em;
      text-transform: uppercase;
    }

    .section-title {
      margin: 0;
      font-size: clamp(28px, 4vw, 38px);
      line-height: 1.1;
      letter-spacing: -0.05em;
      color: var(--text);
    }

    .section-sub {
      margin: 8px 0 0;
      font-size: 15px;
      color: var(--muted);
      max-width: 760px;
    }

    .section-card {
      padding: 28px;
    }

    .intro-grid {
      display: grid;
      grid-template-columns: 1.05fr 0.95fr;
      gap: 18px;
    }

    .intro-copy {
      font-size: 16px;
      color: var(--muted);
    }

    .intro-copy p {
      margin: 0 0 14px;
    }

    .value-list {
      display: grid;
      gap: 12px;
      margin-top: 4px;
    }

    .value-item {
      padding: 16px 18px;
      border-radius: 18px;
      background: var(--card);
      border: 1px solid var(--line);
    }

    .value-item strong {
      display: block;
      color: var(--text);
      margin-bottom: 6px;
      font-size: 16px;
      letter-spacing: -0.02em;
    }

    .value-item span {
      display: block;
      color: var(--muted);
      font-size: 14px;
    }

    .timeline {
      display: grid;
      gap: 16px;
    }

    .timeline-item {
      padding: 24px;
    }

    .timeline-top {
      display: grid;
      grid-template-columns: 1fr auto;
      gap: 14px;
      align-items: start;
      margin-bottom: 12px;
    }

    .timeline-top h3 {
      margin: 0;
      color: var(--text);
      font-size: 24px;
      letter-spacing: -0.04em;
    }

    .role {
      margin-top: 6px;
      color: var(--subtle);
      font-size: 15px;
      font-weight: 700;
    }

    .date {
      padding: 10px 14px;
      border-radius: 999px;
      background: var(--card);
      border: 1px solid var(--line);
      color: var(--primary);
      font-size: 13px;
      font-weight: 800;
      white-space: nowrap;
    }

    .timeline-desc {
      margin: 0;
      color: var(--muted);
      font-size: 15px;
    }

    .bullet-list {
      margin: 14px 0 0;
      padding-left: 18px;
      color: var(--muted);
    }

    .bullet-list li + li { margin-top: 8px; }

    .project-grid {
      display: grid;
      grid-template-columns: repeat(3, minmax(0, 1fr));
      gap: 18px;
    }

    .project-card {
      padding: 24px;
      position: relative;
      overflow: hidden;
    }

    .project-card::before {
      content: "";
      position: absolute;
      inset: 0 0 auto 0;
      height: 4px;
      background: linear-gradient(90deg, var(--primary), var(--secondary));
    }

    .project-label {
      display: inline-flex;
      align-items: center;
      gap: 8px;
      padding: 8px 12px;
      border-radius: 999px;
      background: var(--card);
      border: 1px solid var(--line);
      color: var(--text);
      font-size: 12px;
      font-weight: 800;
      margin-bottom: 14px;
    }

    .project-card h3 {
      margin: 0 0 10px;
      color: var(--text);
      font-size: 24px;
      line-height: 1.2;
      letter-spacing: -0.04em;
    }

    .project-summary {
      margin: 0 0 14px;
      color: var(--muted);
      font-size: 15px;
    }

    .project-highlight {
      padding: 14px 16px;
      border-radius: 16px;
      background: var(--card);
      border: 1px solid var(--line);
      color: var(--primary);
      font-size: 14px;
      font-weight: 700;
      margin-bottom: 14px;
    }

    .skills-grid,
    .edu-grid {
      display: grid;
      grid-template-columns: repeat(2, minmax(0, 1fr));
      gap: 18px;
      margin-top: 18px;
    }

    .skill-card,
    .edu-card {
      padding: 24px;
    }

    .skill-card h3,
    .edu-card h3 {
      margin: 0 0 12px;
      color: var(--text);
      font-size: 20px;
      letter-spacing: -0.03em;
    }

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

    .chip {
      padding: 9px 12px;
      border-radius: 999px;
      background: var(--card);
      border: 1px solid var(--line);
      color: var(--text);
      font-size: 14px;
      font-weight: 700;
    }

    .edu-type {
      display: inline-block;
      margin-bottom: 10px;
      color: var(--primary);
      font-size: 12px;
      font-weight: 800;
      letter-spacing: 0.08em;
      text-transform: uppercase;
    }

    .edu-card p {
      margin: 0;
      color: var(--muted);
      font-size: 15px;
    }

    .footer {
      padding: 28px 0 44px;
      color: var(--subtle);
      font-size: 14px;
      text-align: center;
    }

    @media (max-width: 1080px) {
      .hero-grid,
      .intro-grid,
      .project-grid,
      .skills-grid,
      .edu-grid {
        grid-template-columns: 1fr;
      }

      .impact-row {
        grid-template-columns: 1fr;
      }
    }

    @media (max-width: 860px) {
      .topbar-inner,
      .section-head,
      .timeline-top {
        grid-template-columns: 1fr;
        display: grid;
      }

      .topbar-inner {
        padding: 14px 0;
      }

      .nav {
        justify-content: flex-start;
      }
    }

    @media (max-width: 640px) {
      .wrap { width: min(calc(100% - 20px), var(--max)); }
      .hero { padding-top: 20px; }
      .hero-grid,
      .section-card,
      .timeline-item,
      .project-card,
      .skill-card,
      .edu-card,
      .profile-card,
      .side-card { padding: 20px; }
      h1 { font-size: 42px; }
      .section-title { font-size: 30px; }
      .timeline-top h3,
      .project-card h3 { font-size: 21px; }
    }