:root {
  --color-bg: #fafafa;
  --color-surface: #ffffff;
  --color-text: #1a1a2e;
  --color-text-secondary: #555;
  --color-accent: #2563eb;
  --color-accent-hover: #1d4ed8;
  --color-border: #e5e7eb;
  --color-tag-bg: #f0f4ff;
  --color-tag-text: #2563eb;
  --color-alt-bg: #f3f4f6;
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --max-width: 900px;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

/* Nav */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  background: rgba(250, 250, 250, 0.9);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border);
  z-index: 100;
}

.nav-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.nav-logo {
  font-weight: 700;
  font-size: 1.25rem;
  color: var(--color-text);
  text-decoration: none;
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--color-accent);
  color: white;
  border-radius: 8px;
}

.nav-links {
  display: flex;
  gap: 32px;
}

.nav-links a {
  color: var(--color-text-secondary);
  text-decoration: none;
  font-size: 0.9rem;
  font-weight: 500;
  transition: color 0.2s;
}

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

/* Hero */
.hero {
  padding: 160px 0 80px;
  background: var(--color-bg);
}

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

.hero-content {
  flex: 1;
}

.hero-image {
  flex-shrink: 0;
}

.hero-image img {
  width: 260px;
  height: 260px;
  object-fit: cover;
  border-radius: 50%;
  border: 4px solid var(--color-accent);
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.15);
}

.hero-greeting {
  font-size: 1rem;
  color: var(--color-accent);
  font-weight: 500;
  margin-bottom: 8px;
}

.hero-name {
  font-size: clamp(2.5rem, 6vw, 3.5rem);
  font-weight: 700;
  line-height: 1.1;
  margin-bottom: 12px;
}

.hero-title {
  font-size: clamp(1.1rem, 3vw, 1.5rem);
  font-weight: 500;
  color: var(--color-text-secondary);
  margin-bottom: 20px;
}

.hero-desc {
  font-size: 1.05rem;
  color: var(--color-text-secondary);
  max-width: 560px;
  margin-bottom: 32px;
  line-height: 1.8;
}

.hero-cta {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  padding: 12px 24px;
  border-radius: 8px;
  font-size: 0.9rem;
  font-weight: 600;
  text-decoration: none;
  transition: all 0.2s;
  border: none;
  cursor: pointer;
}

.btn-primary {
  background: var(--color-accent);
  color: white;
}

.btn-primary:hover {
  background: var(--color-accent-hover);
  transform: translateY(-1px);
}

.btn-secondary {
  background: var(--color-surface);
  color: var(--color-text);
  border: 1px solid var(--color-border);
}

.btn-secondary:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
}

/* Sections */
.section {
  padding: 80px 0;
}

.section-alt {
  background: var(--color-alt-bg);
}

.section-title {
  font-size: 1.75rem;
  font-weight: 700;
  margin-bottom: 48px;
  position: relative;
}

.section-title::after {
  content: '';
  display: block;
  width: 48px;
  height: 3px;
  background: var(--color-accent);
  margin-top: 12px;
  border-radius: 2px;
}

/* About */
.about-grid {
  display: grid;
  grid-template-columns: 2fr 1fr;
  gap: 48px;
  align-items: start;
}

.about-text p {
  margin-bottom: 16px;
  color: var(--color-text-secondary);
}

.about-stats {
  display: flex;
  flex-direction: column;
  gap: 24px;
}

.stat {
  display: flex;
  flex-direction: column;
}

.stat-number {
  font-size: 2rem;
  font-weight: 700;
  color: var(--color-accent);
}

.stat-label {
  font-size: 0.85rem;
  color: var(--color-text-secondary);
}

/* Timeline */
.timeline {
  position: relative;
  padding-left: 32px;
}

.timeline::before {
  content: '';
  position: absolute;
  left: 7px;
  top: 8px;
  bottom: 8px;
  width: 2px;
  background: var(--color-border);
}

.timeline-item {
  position: relative;
  margin-bottom: 40px;
}

.timeline-item:last-child {
  margin-bottom: 0;
}

.timeline-marker {
  position: absolute;
  left: -32px;
  top: 8px;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--color-surface);
  border: 3px solid var(--color-accent);
}

.timeline-content {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 12px;
  padding: 24px;
}

.timeline-header {
  display: flex;
  align-items: baseline;
  gap: 12px;
  flex-wrap: wrap;
  margin-bottom: 4px;
}

.timeline-header h3 {
  font-size: 1.1rem;
  font-weight: 600;
}

.timeline-company {
  font-size: 0.9rem;
  color: var(--color-accent);
  font-weight: 500;
}

.timeline-meta {
  font-size: 0.8rem;
  color: var(--color-text-secondary);
  margin-bottom: 12px;
}

.timeline-desc {
  font-size: 0.9rem;
  color: var(--color-text-secondary);
  margin-bottom: 12px;
}

.timeline-list {
  list-style: none;
  margin-bottom: 12px;
}

.timeline-list li {
  font-size: 0.9rem;
  color: var(--color-text-secondary);
  padding-left: 16px;
  position: relative;
  margin-bottom: 6px;
}

.timeline-list li::before {
  content: '';
  position: absolute;
  left: 0;
  top: 9px;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--color-accent);
  opacity: 0.5;
}

.timeline-tags {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
}

.tag {
  font-size: 0.75rem;
  padding: 4px 10px;
  background: var(--color-tag-bg);
  color: var(--color-tag-text);
  border-radius: 6px;
  font-weight: 500;
}

/* Skills */
.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 32px;
}

.skill-category h3 {
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-text-secondary);
  margin-bottom: 12px;
}

.skill-items {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.skill-item {
  font-size: 0.85rem;
  padding: 6px 14px;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 8px;
  font-weight: 500;
}

/* Open Source */
.oss-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 24px;
}

.oss-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 12px;
  padding: 24px;
}

.oss-link {
  text-decoration: none;
  color: inherit;
  transition: border-color 0.2s, transform 0.2s;
}

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

.oss-card h3 {
  font-size: 1.05rem;
  margin-bottom: 8px;
}

.oss-card p {
  font-size: 0.9rem;
  color: var(--color-text-secondary);
}

/* Contact */
.contact-content {
  max-width: 560px;
}

.contact-content > p {
  font-size: 1.05rem;
  color: var(--color-text-secondary);
  margin-bottom: 32px;
}

.contact-links {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
}

.contact-link {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 20px;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 8px;
  color: var(--color-text);
  text-decoration: none;
  font-size: 0.9rem;
  font-weight: 500;
  transition: all 0.2s;
}

.contact-link:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
  transform: translateY(-1px);
}

/* Footer */
.footer {
  padding: 32px 0;
  text-align: center;
  border-top: 1px solid var(--color-border);
}

.footer p {
  font-size: 0.85rem;
  color: var(--color-text-secondary);
}

/* Responsive */
@media (max-width: 768px) {
  .nav-links {
    gap: 20px;
  }

  .hero {
    padding: 120px 0 60px;
  }

  .hero-inner {
    flex-direction: column;
    text-align: center;
    gap: 32px;
  }

  .hero-cta {
    justify-content: center;
  }

  .hero-image img {
    width: 200px;
    height: 200px;
  }

  .about-grid {
    grid-template-columns: 1fr;
    gap: 32px;
  }

  .about-stats {
    flex-direction: row;
    gap: 32px;
  }

  .section {
    padding: 60px 0;
  }

  .skills-grid {
    grid-template-columns: 1fr 1fr;
  }
}

@media (max-width: 480px) {
  .nav-links a {
    font-size: 0.8rem;
  }

  .nav-links {
    gap: 16px;
  }

  .hero-cta {
    flex-direction: column;
    align-items: center;
  }

  .btn {
    justify-content: center;
  }

  .skills-grid {
    grid-template-columns: 1fr;
  }

  .contact-links {
    flex-direction: column;
  }

  .contact-link {
    justify-content: center;
  }
}