:root {
  --bg: #ffffff;
  --fg: #111111;
  --fg-muted: #666666;
  --fg-subtle: #999999;
  --border: #e5e5e5;
  --accent: #2563eb;
  --accent-hover: #1d4ed8;
  --surface: #f7f7f7;
  --shadow: rgba(0, 0, 0, 0.06);
  --radius: 12px;
  --transition: 0.2s ease;
}

[data-theme="dark"] {
  --bg: #0a0a0a;
  --fg: #f0f0f0;
  --fg-muted: #a0a0a0;
  --fg-subtle: #666666;
  --border: #2a2a2a;
  --accent: #60a5fa;
  --accent-hover: #93c5fd;
  --surface: #141414;
  --shadow: rgba(0, 0, 0, 0.3);
}

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: 80px;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  background: var(--bg);
  color: var(--fg);
  line-height: 1.7;
  transition: background var(--transition), color var(--transition);
}

a {
  color: var(--accent);
  text-decoration: none;
  transition: color var(--transition);
}

a:hover {
  color: var(--accent-hover);
}

.container {
  max-width: 760px;
  margin: 0 auto;
  padding: 0 24px;
}

.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: rgba(var(--bg), 0.85);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  transition: background var(--transition), border-color var(--transition);
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  max-width: 760px;
  margin: 0 auto;
  padding: 14px 24px;
  height: 60px;
}

.nav-brand {
  font-weight: 700;
  font-size: 1.25rem;
  color: var(--fg);
}

.nav-links {
  display: flex;
  gap: 28px;
  list-style: none;
}

.nav-links a {
  font-size: 0.875rem;
  color: var(--fg-muted);
  position: relative;
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--fg);
}

.nav-links a.active::after {
  content: "";
  position: absolute;
  bottom: -4px;
  left: 0;
  width: 100%;
  height: 2px;
  background: var(--accent);
  border-radius: 2px;
}

.theme-toggle,
.nav-menu {
  background: transparent;
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--fg);
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: border-color var(--transition), background var(--transition);
}

.theme-toggle:hover,
.nav-menu:hover {
  background: var(--surface);
}

.nav-menu {
  display: none;
  flex-direction: column;
  gap: 5px;
  padding: 8px;
}

.nav-menu span {
  display: block;
  width: 18px;
  height: 2px;
  background: var(--fg);
  border-radius: 2px;
}

.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  padding: 100px 0 80px;
  border-bottom: 1px solid var(--border);
}

.hero-inner {
  display: flex;
  align-items: center;
  gap: 48px;
}

.hero-main {
  flex: 1;
}

.hero-title {
  font-size: clamp(3rem, 8vw, 5rem);
  font-weight: 800;
  letter-spacing: -0.04em;
  line-height: 1.1;
  margin-bottom: 12px;
}

.hero-subtitle {
  font-size: 1.25rem;
  color: var(--fg-muted);
  margin-bottom: 24px;
}

.hero-lead {
  font-size: 1.125rem;
  color: var(--fg-muted);
  max-width: 540px;
  margin-bottom: 32px;
}

.cta {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 14px 24px;
  background: var(--fg);
  color: var(--bg);
  border-radius: 999px;
  font-weight: 600;
  transition: transform var(--transition), opacity var(--transition);
}

.cta:hover {
  color: var(--bg);
  opacity: 0.85;
  transform: translateY(-2px);
}

.hero-avatar {
  flex-shrink: 0;
  width: 180px;
  height: 180px;
  border-radius: 50%;
  overflow: hidden;
  border: 2px solid var(--border);
  background: var(--surface);
  box-shadow: 0 12px 40px var(--shadow);
}

.hero-avatar img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.section {
  padding: 100px 0;
  border-bottom: 1px solid var(--border);
}

.section-heading {
  display: flex;
  align-items: baseline;
  gap: 24px;
  margin-bottom: 48px;
}

.section-num {
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--fg-subtle);
  letter-spacing: 0.05em;
}

.section-title {
  font-size: 2rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.skill-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 20px;
}

.skill-card {
  padding: 24px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  transition: transform var(--transition), border-color var(--transition);
}

.skill-card:hover {
  transform: translateY(-2px);
  border-color: var(--accent);
}

.skill-card h3 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 8px;
  color: var(--fg);
}

.skill-card p {
  font-size: 0.9375rem;
  color: var(--fg-muted);
}

.timeline {
  display: flex;
  flex-direction: column;
  gap: 40px;
}

.timeline-item {
  display: flex;
  gap: 32px;
}

.timeline-meta {
  flex-shrink: 0;
  width: 140px;
}

.timeline-date {
  font-size: 0.875rem;
  color: var(--fg-subtle);
  font-weight: 500;
}

.timeline-title {
  font-size: 1.25rem;
  font-weight: 600;
  margin-bottom: 4px;
}

.timeline-role {
  font-size: 0.9375rem;
  color: var(--fg-muted);
  margin-bottom: 12px;
}

.timeline-desc {
  font-size: 1rem;
  color: var(--fg-muted);
}

.project-list {
  display: flex;
  flex-direction: column;
  gap: 32px;
}

.project-card {
  padding: 32px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  transition: transform var(--transition), border-color var(--transition);
}

.project-card:hover {
  transform: translateY(-3px);
  border-color: var(--accent);
}

.project-title {
  font-size: 1.25rem;
  font-weight: 600;
  margin-bottom: 8px;
}

.project-meta {
  font-size: 0.875rem;
  color: var(--fg-subtle);
  margin-bottom: 12px;
}

.project-desc {
  color: var(--fg-muted);
  margin-bottom: 16px;
}

.project-points {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.project-points li {
  position: relative;
  padding-left: 20px;
  color: var(--fg-muted);
  font-size: 0.9375rem;
}

.project-points li::before {
  content: "—";
  position: absolute;
  left: 0;
  color: var(--accent);
}

.edu-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 20px;
}

.edu-card {
  padding: 24px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
}

.edu-card h3 {
  font-size: 1.125rem;
  font-weight: 600;
  margin-bottom: 8px;
}

.edu-meta {
  font-size: 0.9375rem;
  color: var(--fg-muted);
}

.contact-card {
  text-align: center;
  padding: 48px 32px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
}

.contact-lead {
  font-size: 1.125rem;
  color: var(--fg-muted);
  max-width: 520px;
  margin: 0 auto 24px;
}

.contact-email {
  font-size: 1.5rem;
  font-weight: 700;
  word-break: break-all;
}

.site-footer {
  padding: 40px 0;
  text-align: center;
  font-size: 0.875rem;
  color: var(--fg-subtle);
}

@media (max-width: 640px) {
  .nav-links {
    display: none;
    position: absolute;
    top: 60px;
    left: 0;
    right: 0;
    flex-direction: column;
    gap: 0;
    background: var(--bg);
    border-bottom: 1px solid var(--border);
    padding: 16px 24px;
  }

  .nav-links.open {
    display: flex;
  }

  .nav-links a {
    padding: 12px 0;
  }

  .nav-menu {
    display: flex;
  }

  .hero {
    padding: 100px 0 60px;
  }

  .hero-inner {
    flex-direction: column-reverse;
    align-items: flex-start;
    gap: 32px;
  }

  .hero-avatar {
    width: 120px;
    height: 120px;
  }

  .section {
    padding: 60px 0;
  }

  .skill-grid,
  .edu-grid {
    grid-template-columns: 1fr;
  }

  .timeline-item {
    flex-direction: column;
    gap: 12px;
  }

  .timeline-meta {
    width: auto;
  }
}