/* ===== CSS Variables ===== */
:root {
  /* Light theme (default) */
  --bg-primary: #ffffff;
  --bg-secondary: #f8fafc;
  --bg-tertiary: #f1f5f9;
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-tertiary: #94a3b8;
  --accent-primary: #0ea5e9;
  --accent-secondary: #0284c7;
  --accent-bg: #e0f2fe;
  --border-color: #e2e8f0;
  --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);
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', monospace;
  --transition: all 0.2s ease;
}

/* Dark theme */
[data-theme="dark"] {
  --bg-primary: #0f172a;
  --bg-secondary: #1e293b;
  --bg-tertiary: #334155;
  --text-primary: #f8fafc;
  --text-secondary: #cbd5e1;
  --text-tertiary: #64748b;
  --accent-primary: #38bdf8;
  --accent-secondary: #7dd3fc;
  --accent-bg: #0c4a6e;
  --border-color: #334155;
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.3);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.4), 0 2px 4px -2px rgb(0 0 0 / 0.4);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.5), 0 4px 6px -4px rgb(0 0 0 / 0.5);
}

/* Auto theme (follows system) */
@media (prefers-color-scheme: dark) {
  [data-theme="auto"] {
    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-tertiary: #334155;
    --text-primary: #f8fafc;
    --text-secondary: #cbd5e1;
    --text-tertiary: #64748b;
    --accent-primary: #38bdf8;
    --accent-secondary: #7dd3fc;
    --accent-bg: #0c4a6e;
    --border-color: #334155;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.3);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.4), 0 2px 4px -2px rgb(0 0 0 / 0.4);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.5), 0 4px 6px -4px rgb(0 0 0 / 0.5);
  }
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  transition: background-color 0.3s ease, color 0.3s ease;
}

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

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

img {
  max-width: 100%;
  height: auto;
}

/* ===== Layout ===== */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 1.5rem;
}

.main {
  flex: 1;
}

/* ===== Header ===== */
.header {
  position: sticky;
  top: 0;
  background-color: var(--bg-primary);
  border-bottom: 1px solid var(--border-color);
  backdrop-filter: blur(10px);
  z-index: 100;
  transition: var(--transition);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-weight: 700;
  font-size: 1.25rem;
  color: var(--text-primary);
}

.logo-icon {
  font-size: 1.5rem;
}

.logo:hover {
  color: var(--accent-primary);
}

.nav {
  display: flex;
  gap: 2rem;
}

.nav-link {
  color: var(--text-secondary);
  font-weight: 500;
  font-size: 0.9375rem;
  padding: 0.5rem 0;
  position: relative;
}

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

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

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

/* Theme Toggle */
.theme-toggle {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 0.5rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  transition: var(--transition);
}

.theme-toggle:hover {
  background: var(--bg-tertiary);
  border-color: var(--accent-primary);
}

.theme-toggle-light,
.theme-toggle-dark {
  position: absolute;
  transition: opacity 0.3s ease, transform 0.3s ease;
}

[data-theme="light"] .theme-toggle-light,
[data-theme="auto"] .theme-toggle-light {
  opacity: 1;
  transform: scale(1);
}

[data-theme="light"] .theme-toggle-dark,
[data-theme="auto"] .theme-toggle-dark {
  opacity: 0;
  transform: scale(0.8);
}

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

[data-theme="dark"] .theme-toggle-light {
  opacity: 0;
  transform: scale(0.8);
}

@media (prefers-color-scheme: dark) {
  [data-theme="auto"] .theme-toggle-dark {
    opacity: 1;
    transform: scale(1);
  }
  [data-theme="auto"] .theme-toggle-light {
    opacity: 0;
    transform: scale(0.8);
  }
}

/* Mobile Menu */
.mobile-menu-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 0.5rem;
}

.mobile-menu-toggle span {
  width: 24px;
  height: 2px;
  background-color: var(--text-primary);
  transition: var(--transition);
}

@media (max-width: 768px) {
  .nav {
    position: fixed;
    top: 64px;
    left: 0;
    right: 0;
    background-color: var(--bg-primary);
    border-bottom: 1px solid var(--border-color);
    flex-direction: column;
    padding: 1.5rem;
    gap: 1rem;
    transform: translateY(-100%);
    opacity: 0;
    visibility: hidden;
    transition: var(--transition);
  }
  
  .nav.mobile-open {
    transform: translateY(0);
    opacity: 1;
    visibility: visible;
  }
  
  .mobile-menu-toggle {
    display: flex;
  }
  
  .mobile-menu-toggle.active span:nth-child(1) {
    transform: rotate(45deg) translate(5px, 5px);
  }
  
  .mobile-menu-toggle.active span:nth-child(2) {
    opacity: 0;
  }
  
  .mobile-menu-toggle.active span:nth-child(3) {
    transform: rotate(-45deg) translate(5px, -5px);
  }
}

/* ===== Footer ===== */
.footer {
  background-color: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  padding: 3rem 0 1.5rem;
  margin-top: auto;
}

.footer-inner {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 2rem;
  margin-bottom: 2rem;
}

.footer-title {
  font-weight: 700;
  font-size: 1.125rem;
  margin-bottom: 0.5rem;
}

.footer-desc {
  color: var(--text-secondary);
  font-size: 0.9375rem;
  max-width: 400px;
}

.footer-links {
  display: flex;
  gap: 1rem;
}

.footer-link {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  color: var(--text-secondary);
  font-weight: 500;
}

.footer-link svg {
  width: 20px;
  height: 20px;
}

.footer-link:hover {
  color: var(--accent-primary);
}

.footer-bottom {
  text-align: center;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border-color);
  color: var(--text-tertiary);
  font-size: 0.875rem;
}

@media (max-width: 768px) {
  .footer-inner {
    grid-template-columns: 1fr;
    text-align: center;
  }
  
  .footer-desc {
    max-width: none;
  }
  
  .footer-links {
    justify-content: center;
  }
}

/* ===== Hero Section ===== */
.hero {
  padding: 6rem 0 4rem;
  text-align: center;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background-color: var(--accent-bg);
  color: var(--accent-primary);
  padding: 0.5rem 1rem;
  border-radius: var(--radius-lg);
  font-size: 0.875rem;
  font-weight: 500;
  margin-bottom: 1.5rem;
}

.hero-title {
  font-size: clamp(2.5rem, 5vw, 4rem);
  font-weight: 700;
  line-height: 1.1;
  margin-bottom: 1rem;
  background: linear-gradient(135deg, var(--text-primary) 0%, var(--accent-primary) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-subtitle {
  font-size: 1.25rem;
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto 2rem;
}

.hero-actions {
  display: flex;
  gap: 1rem;
  justify-content: center;
  flex-wrap: wrap;
}

/* ===== Buttons ===== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.75rem 1.5rem;
  border-radius: var(--radius-md);
  font-weight: 600;
  font-size: 0.9375rem;
  transition: var(--transition);
  cursor: pointer;
  border: none;
}

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

.btn-primary:hover {
  background-color: var(--accent-secondary);
  color: white;
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

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

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

/* ===== Section ===== */
.section {
  padding: 4rem 0;
}

.section-header {
  text-align: center;
  margin-bottom: 3rem;
}

.section-title {
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
}

.section-subtitle {
  color: var(--text-secondary);
}

/* ===== Cards ===== */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 1.5rem;
}

.card {
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  transition: var(--transition);
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: var(--accent-primary);
}

.card-icon {
  font-size: 2rem;
  margin-bottom: 1rem;
}

.card-title {
  font-size: 1.125rem;
  font-weight: 600;
  margin-bottom: 0.5rem;
}

.card-desc {
  color: var(--text-secondary);
  font-size: 0.9375rem;
  margin-bottom: 1rem;
}

.card-meta {
  display: flex;
  gap: 1rem;
  font-size: 0.875rem;
  color: var(--text-tertiary);
}

/* ===== Tags ===== */
.tag {
  display: inline-block;
  background-color: var(--accent-bg);
  color: var(--accent-primary);
  padding: 0.25rem 0.75rem;
  border-radius: var(--radius-sm);
  font-size: 0.75rem;
  font-weight: 600;
}

/* ===== Content ===== */
.content {
  max-width: 800px;
  margin: 0 auto;
  padding: 3rem 0;
}

.content h1 {
  font-size: 2.5rem;
  margin-bottom: 1rem;
}

.content h2 {
  font-size: 1.75rem;
  margin: 2rem 0 1rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--border-color);
}

.content h3 {
  font-size: 1.375rem;
  margin: 1.5rem 0 0.75rem;
}

.content p {
  margin-bottom: 1rem;
  color: var(--text-secondary);
}

.content ul,
.content ol {
  margin: 1rem 0 1rem 1.5rem;
  color: var(--text-secondary);
}

.content li {
  margin-bottom: 0.5rem;
}

.content code {
  background-color: var(--bg-tertiary);
  padding: 0.2rem 0.4rem;
  border-radius: var(--radius-sm);
  font-family: var(--font-mono);
  font-size: 0.875rem;
}

.content pre {
  background-color: var(--bg-tertiary);
  padding: 1.5rem;
  border-radius: var(--radius-md);
  overflow-x: auto;
  margin: 1.5rem 0;
}

.content pre code {
  background: none;
  padding: 0;
}

.content blockquote {
  border-left: 4px solid var(--accent-primary);
  padding-left: 1rem;
  margin: 1.5rem 0;
  color: var(--text-secondary);
  font-style: italic;
}

.content img {
  border-radius: var(--radius-md);
  margin: 1.5rem 0;
}

/* ===== Page Header ===== */
.page-header {
  background-color: var(--bg-secondary);
  padding: 4rem 0 2rem;
  margin-bottom: 2rem;
}

.page-title {
  font-size: 2.5rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
}

.page-subtitle {
  color: var(--text-secondary);
  font-size: 1.125rem;
}

/* ===== About Page ===== */
.about-intro {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 3rem;
  align-items: start;
  margin-bottom: 4rem;
}

.about-avatar {
  width: 200px;
  height: 200px;
  background: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 5rem;
  flex-shrink: 0;
}

.about-content h2 {
  margin-top: 0;
}

.skills-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-top: 1rem;
}

.skill-tag {
  background-color: var(--bg-tertiary);
  color: var(--text-secondary);
  padding: 0.5rem 1rem;
  border-radius: var(--radius-lg);
  font-size: 0.875rem;
  font-weight: 500;
}

@media (max-width: 768px) {
  .about-intro {
    grid-template-columns: 1fr;
    text-align: center;
  }
  
  .about-avatar {
    margin: 0 auto;
  }
  
  .skills-grid {
    justify-content: center;
  }
}

/* ===== Timeline ===== */
.timeline {
  position: relative;
  padding-left: 2rem;
}

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

.timeline-item {
  position: relative;
  padding-bottom: 2rem;
}

.timeline-item::before {
  content: '';
  position: absolute;
  left: -2rem;
  top: 0.5rem;
  width: 12px;
  height: 12px;
  background-color: var(--accent-primary);
  border-radius: 50%;
  margin-left: -5px;
}

.timeline-date {
  font-size: 0.875rem;
  color: var(--accent-primary);
  font-weight: 600;
  margin-bottom: 0.25rem;
}

.timeline-title {
  font-weight: 600;
  margin-bottom: 0.25rem;
}

.timeline-company {
  color: var(--text-secondary);
  font-size: 0.9375rem;
}

/* ===== Post List ===== */
.post-list {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.post-item {
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  transition: var(--transition);
}

.post-item:hover {
  border-color: var(--accent-primary);
  transform: translateX(4px);
}

.post-title {
  font-size: 1.25rem;
  font-weight: 600;
  margin-bottom: 0.5rem;
}

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

.post-title a:hover {
  color: var(--accent-primary);
}

.post-meta {
  display: flex;
  gap: 1rem;
  font-size: 0.875rem;
  color: var(--text-tertiary);
  margin-bottom: 0.75rem;
}

.post-excerpt {
  color: var(--text-secondary);
  font-size: 0.9375rem;
}

/* ===== Post ===== */
.post-header {
  text-align: center;
  margin-bottom: 3rem;
}

.post-date {
  color: var(--text-tertiary);
  font-size: 0.9375rem;
}

.post-content {
  font-size: 1.0625rem;
  line-height: 1.8;
}

/* ===== Project Card ===== */
.project-card {
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  overflow: hidden;
  transition: var(--transition);
}

.project-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: var(--accent-primary);
}

.project-header {
  background: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
  padding: 2rem;
  color: white;
}

.project-icon {
  font-size: 3rem;
  margin-bottom: 1rem;
}

.project-name {
  font-size: 1.5rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
}

.project-tagline {
  opacity: 0.9;
}

.project-body {
  padding: 1.5rem;
}

.project-stats {
  display: flex;
  gap: 1.5rem;
  margin-bottom: 1rem;
  font-size: 0.875rem;
  color: var(--text-tertiary);
}

.project-desc {
  color: var(--text-secondary);
  margin-bottom: 1.5rem;
}

.project-links {
  display: flex;
  gap: 1rem;
}

/* ===== Utilities ===== */
.text-center { text-align: center; }
.text-gradient {
  background: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.mt-1 { margin-top: 0.5rem; }
.mt-2 { margin-top: 1rem; }
.mt-3 { margin-top: 1.5rem; }
.mt-4 { margin-top: 2rem; }

.mb-1 { margin-bottom: 0.5rem; }
.mb-2 { margin-bottom: 1rem; }
.mb-3 { margin-bottom: 1.5rem; }
.mb-4 { margin-bottom: 2rem; }

/* Language Switcher */
.lang-toggle {
  font-size: 0.9rem;
  padding: 0.5rem 0.75rem;
  border-radius: 4px;
  background: var(--bg-secondary);
  margin-left: 0.5rem;
}

.lang-toggle:hover {
  background: var(--border-color);
}