/* ===== CSS Variables ===== */
:root {
  /* Primary Colors */
  --primary: #2563eb;
  --primary-dark: #1d4ed8;
  --primary-light: #3b82f6;
  
  /* Neutral Colors */
  --text-primary: #1f2937;
  --text-secondary: #6b7280;
  --text-light: #9ca3af;
  --bg-primary: #ffffff;
  --bg-secondary: #f9fafb;
  --bg-tertiary: #f3f4f6;
  --border: #e5e7eb;
  --border-light: #f3f4f6;
  
  /* Accent Colors */
  --accent-green: #10b981;
  --accent-orange: #f59e0b;
  --accent-purple: #8b5cf6;
  --accent-pink: #ec4899;
  
  /* Fonts */
  --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 
               'Helvetica Neue', Arial, 'Noto Sans SC', 'PingFang SC', 
               'Microsoft YaHei', sans-serif;
  --font-mono: 'SF Mono', Monaco, 'Cascadia Code', 'Roboto Mono', 
               Consolas, 'Courier New', monospace;
  
  /* Spacing */
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;
  --space-24: 6rem;
  
  /* Border Radius */
  --radius-sm: 0.25rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  --radius-2xl: 1.5rem;
  --radius-full: 9999px;
  
  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
  --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);
  
  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-normal: 250ms ease;
  --transition-slow: 350ms ease;
  
  /* Container */
  --container-max: 1200px;
  --container-padding: var(--space-6);
}

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

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  font-size: 1rem;
  line-height: 1.6;
  color: var(--text-primary);
  background-color: var(--bg-primary);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

img, picture, video, canvas, svg {
  display: block;
  max-width: 100%;
}

input, button, textarea, select {
  font: inherit;
}

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

a:hover {
  color: var(--primary-dark);
}

ul, ol {
  list-style: none;
}

/* ===== Utility Classes ===== */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--container-padding);
}

.section {
  padding: var(--space-16) 0;
}

.section-title {
  font-size: 2rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: var(--space-8);
  text-align: center;
}

.section-title::after {
  content: '';
  display: block;
  width: 60px;
  height: 4px;
  background: var(--primary);
  margin: var(--space-4) auto 0;
  border-radius: var(--radius-full);
}

/* ===== Navigation ===== */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid transparent;
  transition: all var(--transition-normal);
}

.navbar.scrolled {
  border-bottom-color: var(--border);
  box-shadow: var(--shadow-sm);
}

.navbar .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 70px;
}

.navbar-brand {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text-primary);
}

.navbar-brand:hover {
  color: var(--primary);
}

.navbar-menu {
  display: flex;
  align-items: center;
  gap: var(--space-8);
}

.navbar-link {
  font-size: 0.95rem;
  font-weight: 500;
  color: var(--text-secondary);
  padding: var(--space-2) 0;
  position: relative;
}

.navbar-link::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--primary);
  transition: width var(--transition-normal);
}

.navbar-link:hover,
.navbar-link.active {
  color: var(--primary);
}

.navbar-link:hover::after,
.navbar-link.active::after {
  width: 100%;
}

.navbar-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  padding: var(--space-2);
  background: none;
  border: none;
  cursor: pointer;
}

.navbar-toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--text-primary);
  transition: all var(--transition-fast);
}

/* ===== Hero Section ===== */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding-top: 70px;
  background: linear-gradient(135deg, var(--bg-primary) 0%, var(--bg-secondary) 100%);
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: -50%;
  right: -20%;
  width: 600px;
  height: 600px;
  background: radial-gradient(circle, rgba(37, 99, 235, 0.08) 0%, transparent 70%);
  border-radius: 50%;
}

.hero::after {
  content: '';
  position: absolute;
  bottom: -30%;
  left: -10%;
  width: 400px;
  height: 400px;
  background: radial-gradient(circle, rgba(139, 92, 246, 0.06) 0%, transparent 70%);
  border-radius: 50%;
}

.hero-content {
  text-align: center;
  position: relative;
  z-index: 1;
}

.hero-avatar {
  width: 150px;
  height: 150px;
  border-radius: 50%;
  margin: 0 auto var(--space-6);
  background: linear-gradient(135deg, var(--primary) 0%, var(--accent-purple) 100%);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 4rem;
  color: white;
  box-shadow: var(--shadow-xl);
  animation: float 3s ease-in-out infinite;
}

@keyframes float {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-10px); }
}

.hero-avatar img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  border-radius: 50%;
}

.hero-title {
  font-size: 3rem;
  font-weight: 800;
  color: var(--text-primary);
  margin-bottom: var(--space-3);
  animation: fadeInUp 0.6s ease-out;
}

.hero-subtitle {
  font-size: 1.5rem;
  font-weight: 500;
  color: var(--primary);
  margin-bottom: var(--space-4);
  animation: fadeInUp 0.6s ease-out 0.1s both;
}

.hero-description {
  font-size: 1.125rem;
  color: var(--text-secondary);
  max-width: 500px;
  margin: 0 auto var(--space-8);
  animation: fadeInUp 0.6s ease-out 0.2s both;
}

.hero-social {
  display: flex;
  justify-content: center;
  gap: var(--space-4);
  animation: fadeInUp 0.6s ease-out 0.3s both;
}

.social-link {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 48px;
  height: 48px;
  border-radius: var(--radius-lg);
  background: var(--bg-primary);
  color: var(--text-secondary);
  border: 1px solid var(--border);
  transition: all var(--transition-fast);
}

.social-link:hover {
  color: var(--primary);
  border-color: var(--primary);
  transform: translateY(-3px);
  box-shadow: var(--shadow-md);
}

.social-link svg {
  width: 24px;
  height: 24px;
}

@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ===== Skills Section ===== */
.skills {
  background: var(--bg-secondary);
}

.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--space-6);
}

.skill-category {
  background: var(--bg-primary);
  border-radius: var(--radius-xl);
  padding: var(--space-6);
  border: 1px solid var(--border);
  transition: all var(--transition-normal);
}

.skill-category:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-lg);
  border-color: var(--primary);
}

.skill-category-title {
  font-size: 1.125rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: var(--space-4);
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.skill-category-title svg {
  width: 24px;
  height: 24px;
  color: var(--primary);
}

.skill-tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

.skill-tag {
  display: inline-flex;
  align-items: center;
  padding: var(--space-2) var(--space-3);
  background: var(--bg-secondary);
  color: var(--text-secondary);
  font-size: 0.875rem;
  font-weight: 500;
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
}

.skill-tag:hover {
  background: var(--primary);
  color: white;
}

/* ===== Projects Section ===== */
.projects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
  gap: var(--space-6);
}

.project-card {
  background: var(--bg-primary);
  border-radius: var(--radius-xl);
  border: 1px solid var(--border);
  overflow: hidden;
  transition: all var(--transition-normal);
}

.project-card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-xl);
  border-color: var(--primary);
}

.project-image {
  width: 100%;
  height: 200px;
  background: linear-gradient(135deg, var(--bg-secondary) 0%, var(--bg-tertiary) 100%);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-light);
  font-size: 3rem;
  position: relative;
  overflow: hidden;
}

.project-image::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, rgba(37, 99, 235, 0.1) 0%, rgba(139, 92, 246, 0.1) 100%);
}

.project-image img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.project-content {
  padding: var(--space-6);
}

.project-title {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: var(--space-2);
}

.project-description {
  font-size: 0.95rem;
  color: var(--text-secondary);
  margin-bottom: var(--space-4);
  line-height: 1.6;
}

.project-tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin-bottom: var(--space-4);
}

.project-tag {
  font-size: 0.75rem;
  font-weight: 500;
  padding: var(--space-1) var(--space-2);
  background: var(--bg-secondary);
  color: var(--primary);
  border-radius: var(--radius-sm);
}

.project-links {
  display: flex;
  gap: var(--space-3);
}

.project-link {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-4);
  font-size: 0.875rem;
  font-weight: 500;
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
}

.project-link-primary {
  background: var(--primary);
  color: white;
}

.project-link-primary:hover {
  background: var(--primary-dark);
  color: white;
}

.project-link-secondary {
  background: var(--bg-secondary);
  color: var(--text-secondary);
}

.project-link-secondary:hover {
  background: var(--bg-tertiary);
  color: var(--text-primary);
}

.project-link svg {
  width: 16px;
  height: 16px;
}

/* ===== Contact Section ===== */
.contact {
  background: var(--bg-secondary);
}

.contact-content {
  max-width: 600px;
  margin: 0 auto;
  text-align: center;
}

.contact-description {
  font-size: 1.125rem;
  color: var(--text-secondary);
  margin-bottom: var(--space-8);
}

.contact-links {
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
}

.contact-item {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-3);
  padding: var(--space-4) var(--space-6);
  background: var(--bg-primary);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border);
  color: var(--text-primary);
  font-size: 1rem;
  transition: all var(--transition-fast);
}

.contact-item:hover {
  border-color: var(--primary);
  color: var(--primary);
  transform: translateX(5px);
}

.contact-item svg {
  width: 24px;
  height: 24px;
  color: var(--primary);
}

/* ===== Footer ===== */
.footer {
  padding: var(--space-8) 0;
  text-align: center;
  border-top: 1px solid var(--border);
}

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

.footer-text a {
  color: var(--primary);
}

/* ===== Scroll Animation ===== */
.fade-in {
  opacity: 0;
  transform: translateY(30px);
  transition: all 0.6s ease-out;
}

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

/* ===== Responsive Design ===== */
@media (max-width: 768px) {
  :root {
    --container-padding: var(--space-4);
  }
  
  .navbar-menu {
    position: fixed;
    top: 70px;
    left: 0;
    right: 0;
    background: var(--bg-primary);
    flex-direction: column;
    padding: var(--space-6);
    gap: var(--space-4);
    border-bottom: 1px solid var(--border);
    transform: translateY(-100%);
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-normal);
  }
  
  .navbar-menu.active {
    transform: translateY(0);
    opacity: 1;
    visibility: visible;
  }
  
  .navbar-toggle {
    display: flex;
  }
  
  .navbar-toggle.active span:nth-child(1) {
    transform: rotate(45deg) translate(5px, 5px);
  }
  
  .navbar-toggle.active span:nth-child(2) {
    opacity: 0;
  }
  
  .navbar-toggle.active span:nth-child(3) {
    transform: rotate(-45deg) translate(5px, -5px);
  }
  
  .hero-title {
    font-size: 2rem;
  }
  
  .hero-subtitle {
    font-size: 1.25rem;
  }
  
  .hero-description {
    font-size: 1rem;
  }
  
  .section-title {
    font-size: 1.5rem;
  }
  
  .projects-grid {
    grid-template-columns: 1fr;
  }
  
  .skills-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 480px) {
  .hero-avatar {
    width: 120px;
    height: 120px;
    font-size: 3rem;
  }
  
  .hero-title {
    font-size: 1.75rem;
  }
  
  .hero-social {
    flex-wrap: wrap;
  }
  
  .project-links {
    flex-direction: column;
  }
  
  .project-link {
    justify-content: center;
  }
}