/* ===== Reset & Base ===== */
*, *::before, *::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  --font-stack: -apple-system, 'SF Pro Text', 'SF Pro Display', 'Helvetica Neue', Helvetica, Arial, sans-serif;
  --radius-pill: 980px;
  --radius-card: 16px;
  --radius-sm: 10px;
  --transition: 0.35s cubic-bezier(0.25, 0.1, 0.25, 1);
  --max-width: 800px;
  --header-height: 56px;
}

[data-theme="dark"] {
  --bg: #1c1c1e;
  --bg-card: #2c2c2e;
  --bg-header: rgba(28, 28, 30, 0.8);
  --text-primary: #f5f5f7;
  --text-secondary: #98989d;
  --text-tertiary: #636366;
  --border: #38383a;
  --accent: #0a84ff;
  --accent-hover: #409cff;
  --shadow: 0 2px 12px rgba(0,0,0,0.3);
  --shadow-lg: 0 8px 30px rgba(0,0,0,0.4);
}

[data-theme="light"] {
  --bg: #f5f5f7;
  --bg-card: #ffffff;
  --bg-header: rgba(245, 245, 247, 0.8);
  --text-primary: #1d1d1f;
  --text-secondary: #6e6e73;
  --text-tertiary: #aeaeb2;
  --border: #d2d2d7;
  --accent: #0071e3;
  --accent-hover: #0077ed;
  --shadow: 0 2px 12px rgba(0,0,0,0.08);
  --shadow-lg: 0 8px 30px rgba(0,0,0,0.12);
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-stack);
  background: var(--bg);
  color: var(--text-primary);
  line-height: 1.6;
  transition: background var(--transition), color var(--transition);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* ===== Header ===== */
.header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--bg-header);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border);
  transition: background var(--transition), border-color var(--transition);
}

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

.logo {
  font-weight: 700;
  font-size: 1.1rem;
  letter-spacing: -0.02em;
  color: var(--text-primary);
  transition: color var(--transition);
}

.nav-links {
  display: flex;
  gap: 20px;
}

.nav-links a {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.85rem;
  font-weight: 500;
  transition: color var(--transition);
}

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

.theme-toggle {
  background: none;
  border: 1px solid var(--border);
  border-radius: var(--radius-pill);
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  font-size: 1rem;
  transition: background var(--transition), border-color var(--transition), transform 0.2s;
  position: relative;
}

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

.theme-toggle .icon-sun,
.theme-toggle .icon-moon {
  position: absolute;
  transition: opacity 0.35s ease, transform 0.35s ease;
}

[data-theme="dark"] .theme-toggle .icon-sun {
  opacity: 0;
  transform: rotate(-90deg) scale(0.5);
}

[data-theme="dark"] .theme-toggle .icon-moon {
  opacity: 1;
  transform: rotate(0) scale(1);
}

[data-theme="light"] .theme-toggle .icon-sun {
  opacity: 1;
  transform: rotate(0) scale(1);
}

[data-theme="light"] .theme-toggle .icon-moon {
  opacity: 0;
  transform: rotate(90deg) scale(0.5);
}

/* ===== Hero ===== */
.hero {
  min-height: calc(100vh - var(--header-height));
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 80px 24px;
  text-align: center;
}

.hero-content {
  max-width: 680px;
  animation: fadeInUp 0.8s ease forwards;
}

.hero-avatar {
  width: 96px;
  height: 96px;
  border-radius: 50%;
  background: var(--accent);
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 24px;
  box-shadow: 0 0 0 3px var(--bg-card), 0 0 0 5px var(--border);
  transition: box-shadow var(--transition), background var(--transition);
}

.hero-avatar-initials {
  font-size: 2rem;
  font-weight: 700;
  color: #ffffff;
  letter-spacing: 0.02em;
}

.hero-location {
  font-size: 0.9rem;
  color: var(--text-secondary);
  margin-bottom: 16px;
  letter-spacing: 0.02em;
  transition: color var(--transition);
}

.hero-name {
  font-size: clamp(2.8rem, 6vw, 4.5rem);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.1;
  margin-bottom: 12px;
  color: var(--text-primary);
  transition: color var(--transition);
}

.hero-title {
  font-size: clamp(1rem, 2vw, 1.2rem);
  font-weight: 500;
  color: var(--text-secondary);
  margin-bottom: 12px;
  transition: color var(--transition);
}

.hero-subtitle {
  font-size: 1rem;
  color: var(--text-tertiary);
  max-width: 520px;
  margin: 0 auto 28px;
  line-height: 1.7;
  transition: color var(--transition);
}

.hero-social {
  display: flex;
  justify-content: center;
  gap: 16px;
  margin-bottom: 32px;
}

.hero-social-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  border: 1px solid var(--border);
  color: var(--text-secondary);
  transition: all var(--transition);
}

.hero-social-link:hover {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--bg-card);
  transform: translateY(-2px);
}

.hero-actions {
  display: flex;
  gap: 12px;
  justify-content: center;
  flex-wrap: wrap;
}

/* ===== Pill Buttons ===== */
.pill-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 12px 28px;
  border-radius: var(--radius-pill);
  font-size: 0.9rem;
  font-weight: 500;
  text-decoration: none;
  transition: all var(--transition);
  font-family: inherit;
  cursor: pointer;
}

.pill-btn.primary {
  background: var(--accent);
  color: #ffffff;
  border: none;
}

.pill-btn.primary:hover {
  background: var(--accent-hover);
  transform: scale(1.02);
}

.pill-btn.secondary {
  background: transparent;
  color: var(--accent);
  border: 1px solid var(--border);
}

.pill-btn.secondary:hover {
  background: var(--bg-card);
  border-color: var(--accent);
}

/* ===== Sections ===== */
.section {
  padding: 100px 24px;
}

.section:nth-of-type(even) {
  background: var(--bg-card);
  transition: background var(--transition);
}

.section-inner {
  max-width: var(--max-width);
  margin: 0 auto;
}

.section-title {
  font-size: clamp(1.8rem, 3vw, 2.4rem);
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 48px;
  color: var(--text-primary);
  transition: color var(--transition);
}

/* ===== About ===== */
.about-bio {
  font-size: 1.15rem;
  line-height: 1.8;
  color: var(--text-secondary);
  max-width: 640px;
  margin-bottom: 48px;
  transition: color var(--transition);
}

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

.about-details h3 {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-tertiary);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: 16px;
  transition: color var(--transition);
}

.edu-degree {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 4px;
  transition: color var(--transition);
}

.edu-school {
  font-size: 0.9rem;
  color: var(--text-secondary);
  transition: color var(--transition);
}

.focus-block {
  font-family: 'SF Mono', 'Menlo', 'Monaco', 'Courier New', monospace;
  font-size: 0.9rem;
  margin-bottom: 8px;
  display: flex;
  gap: 6px;
}

.focus-key {
  color: var(--accent);
}

.focus-op {
  color: var(--text-tertiary);
}

.focus-val {
  color: #a9b665;
}

/* ===== Timeline ===== */
.timeline {
  display: flex;
  flex-direction: column;
  gap: 0;
  position: relative;
}

.timeline::before {
  content: '';
  position: absolute;
  left: 20px;
  top: 0;
  bottom: 0;
  width: 2px;
  background: var(--border);
  transition: background var(--transition);
}

.timeline-item {
  position: relative;
  padding: 0 0 48px 56px;
  animation: fadeInUp 0.6s ease forwards;
  opacity: 0;
}

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

.timeline-dot {
  position: absolute;
  left: 12px;
  top: 6px;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: var(--accent);
  border: 3px solid var(--bg);
  transition: background var(--transition), border-color var(--transition);
  z-index: 1;
}

.timeline-period {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 6px;
  transition: color var(--transition);
}

.timeline-title {
  font-size: 1.2rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 2px;
  transition: color var(--transition);
}

.timeline-company {
  font-size: 1rem;
  color: var(--text-secondary);
  margin-bottom: 10px;
  transition: color var(--transition);
}

.timeline-tech {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.timeline-tech span {
  font-size: 0.78rem;
  padding: 4px 12px;
  border-radius: var(--radius-pill);
  background: var(--accent);
  color: #ffffff;
  font-weight: 500;
  transition: background var(--transition);
}

/* ===== Projects ===== */
.projects-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
}

.project-card {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-card);
  overflow: hidden;
  transition: all var(--transition);
  animation: fadeInUp 0.6s ease forwards;
  opacity: 0;
}

.project-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
}

.project-body {
  padding: 28px;
}

.project-body h3 {
  font-size: 1.15rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 10px;
  transition: color var(--transition);
}

.project-body p {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.7;
  margin-bottom: 18px;
  transition: color var(--transition);
}

.project-tech {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.project-tech span {
  font-size: 0.75rem;
  padding: 4px 10px;
  border-radius: var(--radius-pill);
  background: var(--bg-card);
  color: var(--text-secondary);
  border: 1px solid var(--border);
  font-weight: 500;
  transition: all var(--transition);
}

/* ===== Skills Grid ===== */
.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 24px;
}

.skill-category {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-card);
  padding: 28px;
  box-shadow: var(--shadow);
  transition: background var(--transition), border-color var(--transition), box-shadow var(--transition), transform 0.3s ease;
  animation: fadeInUp 0.6s ease forwards;
  opacity: 0;
}

.skill-category:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.skill-category h3 {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 16px;
  letter-spacing: -0.01em;
  transition: color var(--transition);
}

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

.skill-tags span {
  font-size: 0.8rem;
  padding: 6px 14px;
  border-radius: var(--radius-pill);
  background: var(--bg);
  color: var(--text-secondary);
  border: 1px solid var(--border);
  font-weight: 500;
  transition: background var(--transition), color var(--transition), border-color var(--transition);
}

/* ===== Contact ===== */
.contact-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 48px;
  align-items: start;
}

.contact-item {
  margin-bottom: 24px;
}

.contact-label {
  display: block;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-tertiary);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: 6px;
  transition: color var(--transition);
}

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

.contact-item a:hover {
  text-decoration: underline;
}

.contact-item > span {
  color: var(--text-secondary);
  font-size: 0.95rem;
  transition: color var(--transition);
}

.contact-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 4px;
}

.contact-tags span {
  font-size: 0.8rem;
  padding: 4px 12px;
  border-radius: var(--radius-pill);
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--text-secondary);
  font-weight: 500;
  transition: all var(--transition);
}

.contact-response {
  font-size: 0.85rem;
  color: var(--text-tertiary);
  font-style: italic;
  margin-top: 16px;
  transition: color var(--transition);
}

.contact-form {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.contact-form input,
.contact-form textarea {
  font-family: inherit;
  font-size: 0.95rem;
  padding: 14px 18px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--bg);
  color: var(--text-primary);
  outline: none;
  transition: all var(--transition);
  resize: vertical;
}

.contact-form input:focus,
.contact-form textarea:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(10, 132, 255, 0.15);
}

.contact-form input::placeholder,
.contact-form textarea::placeholder {
  color: var(--text-tertiary);
}

.contact-form .pill-btn {
  align-self: flex-start;
}

/* ===== Footer ===== */
.footer {
  padding: 60px 24px 40px;
  text-align: center;
  border-top: 1px solid var(--border);
  transition: border-color var(--transition);
}

.social-links {
  display: flex;
  justify-content: center;
  gap: 24px;
  margin-bottom: 20px;
}

.social-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.9rem;
  font-weight: 500;
  padding: 8px 16px;
  border-radius: var(--radius-pill);
  border: 1px solid var(--border);
  transition: all var(--transition);
}

.social-link:hover {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--bg-card);
  transform: translateY(-1px);
}

.footer-copy {
  font-size: 0.8rem;
  color: var(--text-tertiary);
  transition: color var(--transition);
}

/* ===== Animations ===== */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(24px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.hero-content {
  animation: fadeInUp 0.8s ease forwards;
}

.timeline-item:nth-child(1) { animation-delay: 0.1s; }
.timeline-item:nth-child(2) { animation-delay: 0.2s; }
.timeline-item:nth-child(3) { animation-delay: 0.3s; }
.timeline-item:nth-child(4) { animation-delay: 0.4s; }

.project-card:nth-child(1) { animation-delay: 0.05s; }
.project-card:nth-child(2) { animation-delay: 0.1s; }
.project-card:nth-child(3) { animation-delay: 0.15s; }
.project-card:nth-child(4) { animation-delay: 0.2s; }

.skill-category:nth-child(1) { animation-delay: 0.05s; }
.skill-category:nth-child(2) { animation-delay: 0.1s; }
.skill-category:nth-child(3) { animation-delay: 0.15s; }
.skill-category:nth-child(4) { animation-delay: 0.2s; }
.skill-category:nth-child(5) { animation-delay: 0.25s; }

/* ===== Responsive ===== */
@media (max-width: 640px) {
  .header-inner {
    padding: 0 16px;
  }

  .nav-links {
    gap: 12px;
  }

  .nav-links a {
    font-size: 0.78rem;
  }

  .hero {
    padding: 60px 16px;
  }

  .section {
    padding: 60px 16px;
  }

  .section-title {
    margin-bottom: 32px;
  }

  .about-details {
    grid-template-columns: 1fr;
    gap: 24px;
  }

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

  .timeline-item {
    padding-left: 44px;
  }

  .timeline::before {
    left: 14px;
  }

  .timeline-dot {
    left: 6px;
    width: 14px;
    height: 14px;
  }

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

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

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