/* ===== CSS Variables ===== */
:root {
  --color-bg: #0f1419;
  --color-bg-alt: #1a2332;
  --color-surface: #243044;
  --color-primary: #3b82f6;
  --color-primary-light: #60a5fa;
  --color-accent: #06b6d4;
  --color-text: #e2e8f0;
  --color-text-muted: #94a3b8;
  --color-border: rgba(148, 163, 184, 0.15);
  --font-sans: 'Noto Sans SC', -apple-system, BlinkMacSystemFont, sans-serif;
  --font-mono: 'JetBrains Mono', monospace;
  --radius-lg: 16px;
  --shadow: 0 4px 24px rgba(0, 0, 0, 0.3);
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --header-height: 64px;
}

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: var(--header-height);
}

body {
  font-family: var(--font-sans);
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  overflow-x: hidden;
}

a {
  color: inherit;
  text-decoration: none;
}

ul {
  list-style: none;
}

.container {
  width: 100%;
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 24px;
}

/* ===== Header & Nav ===== */
.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  height: var(--header-height);
  background: rgba(15, 20, 25, 0.85);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border);
  transition: var(--transition);
}

.header.scrolled {
  box-shadow: var(--shadow);
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

.nav-logo {
  font-weight: 700;
  font-size: 1.25rem;
  background: linear-gradient(135deg, var(--color-primary), var(--color-accent));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.nav-menu {
  display: flex;
  gap: 8px;
}

.nav-link {
  padding: 8px 16px;
  border-radius: 8px;
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--color-text-muted);
  transition: var(--transition);
}

.nav-link:hover,
.nav-link.active {
  color: var(--color-text);
  background: var(--color-surface);
}

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 8px;
}

.nav-toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--color-text);
  border-radius: 2px;
  transition: var(--transition);
}

/* ===== Hero ===== */
.hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: calc(var(--header-height) + 40px) 0 80px;
  overflow: hidden;
}

.hero-bg {
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse 80% 50% at 50% -20%, rgba(59, 130, 246, 0.25), transparent),
    radial-gradient(ellipse 60% 40% at 80% 60%, rgba(6, 182, 212, 0.12), transparent),
    radial-gradient(ellipse 50% 30% at 20% 80%, rgba(59, 130, 246, 0.08), transparent);
  pointer-events: none;
}

.hero-content {
  position: relative;
  text-align: center;
  animation: fadeUp 0.8s ease-out;
}

@keyframes fadeUp {
  from {
    opacity: 0;
    transform: translateY(30px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.hero-greeting {
  font-size: 1.1rem;
  color: var(--color-text-muted);
  margin-bottom: 8px;
}

.hero-name {
  font-size: clamp(2.5rem, 6vw, 4rem);
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 12px;
  background: linear-gradient(135deg, #fff 0%, var(--color-text-muted) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-title {
  font-size: 1.25rem;
  color: var(--color-primary-light);
  font-weight: 500;
  margin-bottom: 20px;
}

.hero-desc {
  max-width: 560px;
  margin: 0 auto 32px;
  color: var(--color-text-muted);
  font-size: 1rem;
  line-height: 1.8;
}

.hero-actions {
  display: flex;
  gap: 16px;
  justify-content: center;
  flex-wrap: wrap;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 12px 28px;
  border-radius: 10px;
  font-weight: 600;
  font-size: 0.95rem;
  transition: var(--transition);
  cursor: pointer;
  border: 2px solid transparent;
}

.btn-primary {
  background: linear-gradient(135deg, var(--color-primary), #2563eb);
  color: white;
  box-shadow: 0 4px 16px rgba(59, 130, 246, 0.4);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 24px rgba(59, 130, 246, 0.5);
}

.scroll-hint {
  position: absolute;
  bottom: 32px;
  left: 50%;
  transform: translateX(-50%);
  color: var(--color-text-muted);
  animation: bounce 2s infinite;
}

@keyframes bounce {
  0%, 100% { transform: translateX(-50%) translateY(0); }
  50% { transform: translateX(-50%) translateY(8px); }
}

/* ===== Sections ===== */
.section {
  padding: 100px 0;
}

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

.section-header {
  text-align: center;
  margin-bottom: 56px;
}

.section-tag {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--color-accent);
  text-transform: uppercase;
  letter-spacing: 0.15em;
  margin-bottom: 12px;
}

.section-title {
  font-size: clamp(1.75rem, 4vw, 2.25rem);
  font-weight: 700;
  letter-spacing: -0.02em;
}

/* ===== Card ===== */
.card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 28px;
  transition: var(--transition);
}

.card:hover {
  border-color: rgba(59, 130, 246, 0.3);
  box-shadow: var(--shadow);
}

/* ===== Timeline ===== */
.timeline {
  position: relative;
  max-width: 720px;
  margin: 0 auto;
}

.timeline::before {
  content: '';
  position: absolute;
  left: 7px;
  top: 8px;
  bottom: 8px;
  width: 2px;
  background: linear-gradient(to bottom, var(--color-primary), var(--color-accent));
  border-radius: 2px;
}

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

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

.timeline-marker {
  position: absolute;
  left: 0;
  top: 8px;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--color-primary);
  border: 3px solid var(--color-bg);
  box-shadow: 0 0 0 2px var(--color-primary);
}

.section-alt .timeline-marker {
  border-color: var(--color-bg-alt);
}

.timeline-date {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--color-accent);
  margin-bottom: 8px;
}

.timeline-title {
  font-size: 1.2rem;
  font-weight: 600;
  margin-bottom: 4px;
}

.timeline-subtitle {
  color: var(--color-text-muted);
  font-size: 0.95rem;
  margin-bottom: 12px;
}

.timeline-desc {
  color: var(--color-text-muted);
  font-size: 0.95rem;
  line-height: 1.7;
}

.timeline-list {
  color: var(--color-text-muted);
  font-size: 0.95rem;
}

.timeline-list li {
  position: relative;
  padding-left: 20px;
  margin-bottom: 8px;
  line-height: 1.6;
}

.timeline-list li::before {
  content: '▸';
  position: absolute;
  left: 0;
  color: var(--color-primary);
}

/* ===== Skills ===== */
.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 24px;
}

.skill-category-title {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 1.1rem;
  font-weight: 600;
  margin-bottom: 24px;
}

.skill-icon {
  font-size: 1.3rem;
}

.skill-items {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.skill-info {
  display: flex;
  justify-content: space-between;
  font-size: 0.9rem;
  margin-bottom: 8px;
}

.skill-info span:last-child {
  color: var(--color-text-muted);
  font-family: var(--font-mono);
  font-size: 0.8rem;
}

.skill-bar {
  height: 8px;
  background: var(--color-bg);
  border-radius: 4px;
  overflow: hidden;
}

.skill-progress {
  height: 100%;
  background: linear-gradient(90deg, var(--color-primary), var(--color-accent));
  border-radius: 4px;
  transition: width 1s ease-out;
}

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

.skill-tags span {
  padding: 8px 16px;
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: 8px;
  font-size: 0.85rem;
  font-weight: 500;
  transition: var(--transition);
}

.skill-tags span:hover {
  border-color: var(--color-primary);
  color: var(--color-primary-light);
}

/* ===== Contact ===== */
.contact-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 20px;
  max-width: 900px;
  margin: 0 auto;
}

.contact-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  padding: 32px 24px;
  transition: var(--transition);
}

a.contact-card:hover {
  transform: translateY(-4px);
  border-color: var(--color-primary);
}

.contact-icon {
  font-size: 2rem;
  margin-bottom: 12px;
}

.contact-label {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  margin-bottom: 4px;
}

.contact-value {
  font-weight: 500;
  font-size: 0.95rem;
}

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

.footer p {
  color: var(--color-text-muted);
  font-size: 0.875rem;
}

/* ===== Animations on scroll ===== */
.fade-in {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .nav-toggle {
    display: flex;
  }

  .nav-menu {
    position: fixed;
    top: var(--header-height);
    left: 0;
    right: 0;
    flex-direction: column;
    background: var(--color-bg-alt);
    padding: 16px;
    border-bottom: 1px solid var(--color-border);
    transform: translateY(-120%);
    opacity: 0;
    visibility: hidden;
    transition: var(--transition);
  }

  .nav-menu.open {
    transform: translateY(0);
    opacity: 1;
    visibility: visible;
  }

  .nav-link {
    display: block;
    padding: 12px 16px;
  }

  .section {
    padding: 64px 0;
  }

  .timeline::before {
    left: 5px;
  }

  .timeline-item {
    padding-left: 32px;
  }

  .timeline-marker {
    width: 12px;
    height: 12px;
    left: 0;
  }

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