/* ========== CSS Variables & Theme ========== */
:root {
  /* Light theme (default) */
  --bg-primary: #ffffff;
  --bg-secondary: #f8f9fa;
  --bg-card: #ffffff;
  --text-primary: #1a1a2e;
  --text-secondary: #555;
  --text-muted: #888;
  --accent: #6c63ff;
  --accent-hover: #5a52d5;
  --accent-light: rgba(108, 99, 255, 0.1);
  --border: #eaeaea;
  --shadow: 0 2px 16px rgba(0, 0, 0, 0.08);
  --shadow-hover: 0 8px 30px rgba(0, 0, 0, 0.12);
  --nav-bg: rgba(255, 255, 255, 0.85);
  --code-bg: #f4f4f5;
  --tag-bg: #f0f0ff;
  --tag-color: #6c63ff;
  --input-bg: #f8f9fa;
  --input-border: #ddd;
  --max-width: 960px;
  --radius: 12px;
  --radius-sm: 8px;
  --transition: 0.3s ease;
}

[data-theme="dark"] {
  --bg-primary: #0f0f23;
  --bg-secondary: #1a1a2e;
  --bg-card: #1e1e36;
  --text-primary: #e4e4f0;
  --text-secondary: #a0a0b8;
  --text-muted: #6a6a80;
  --accent: #8b83ff;
  --accent-hover: #a09aff;
  --accent-light: rgba(139, 131, 255, 0.15);
  --border: #2a2a45;
  --shadow: 0 2px 16px rgba(0, 0, 0, 0.3);
  --shadow-hover: 0 8px 30px rgba(0, 0, 0, 0.4);
  --nav-bg: rgba(15, 15, 35, 0.9);
  --code-bg: #2a2a45;
  --tag-bg: rgba(139, 131, 255, 0.15);
  --tag-color: #8b83ff;
  --input-bg: #1a1a2e;
  --input-border: #333;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.7;
  transition: background-color var(--transition), color var(--transition);
  min-height: 100vh;
}

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

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

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

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

.section {
  padding: 80px 0;
}

.section-title {
  font-size: 1.8rem;
  font-weight: 700;
  margin-bottom: 12px;
  text-align: center;
}

.section-subtitle {
  color: var(--text-secondary);
  text-align: center;
  margin-bottom: 48px;
  font-size: 1rem;
}

/* ========== Fade-in Animation ========== */
.fade-in {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

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

/* ========== Navigation ========== */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: var(--nav-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  transition: background var(--transition), border-color var(--transition);
}

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

.nav-logo {
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--text-primary);
}

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

.nav-links {
  display: flex;
  align-items: center;
  gap: 32px;
  list-style: none;
}

.nav-links a {
  color: var(--text-secondary);
  font-size: 0.95rem;
  font-weight: 500;
  position: relative;
}

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

.nav-links a::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--accent);
  transition: width var(--transition);
}

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

/* Theme toggle button */
.theme-toggle {
  background: none;
  border: 2px solid var(--border);
  border-radius: 50%;
  width: 38px;
  height: 38px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  font-size: 1.1rem;
  transition: all var(--transition);
  color: var(--text-primary);
  margin-left: 8px;
}

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

/* Hamburger menu */
.hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  cursor: pointer;
  background: none;
  border: none;
  padding: 4px;
}

.hamburger span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--text-primary);
  border-radius: 2px;
  transition: all var(--transition);
}

.hamburger.active span:nth-child(1) {
  transform: rotate(45deg) translate(5px, 5px);
}

.hamburger.active span:nth-child(2) {
  opacity: 0;
}

.hamburger.active span:nth-child(3) {
  transform: rotate(-45deg) translate(5px, -5px);
}

/* ========== Hero Section ========== */
.hero {
  padding: 160px 0 100px;
  text-align: center;
  min-height: 100vh;
  display: flex;
  align-items: center;
}

.hero-avatar {
  width: 140px;
  height: 140px;
  border-radius: 50%;
  object-fit: cover;
  border: 4px solid var(--accent);
  box-shadow: 0 0 40px var(--accent-light);
  margin-bottom: 24px;
  transition: border-color var(--transition), box-shadow var(--transition);
}

.hero h1 {
  font-size: 2.8rem;
  font-weight: 800;
  margin-bottom: 12px;
  letter-spacing: -0.5px;
}

.hero .highlight {
  color: var(--accent);
}

.hero p {
  font-size: 1.15rem;
  color: var(--text-secondary);
  max-width: 560px;
  margin: 0 auto 32px;
}

/* Social links */
.social-links {
  display: flex;
  justify-content: center;
  gap: 16px;
  margin-bottom: 40px;
}

.social-links a {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  background: var(--bg-secondary);
  color: var(--text-secondary);
  border: 1px solid var(--border);
  transition: all var(--transition);
}

.social-links a:hover {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
  transform: translateY(-3px);
}

.social-links svg {
  width: 20px;
  height: 20px;
}

/* Scroll indicator */
.scroll-indicator {
  position: absolute;
  bottom: 40px;
  left: 50%;
  transform: translateX(-50%);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  color: var(--text-muted);
  font-size: 0.8rem;
  animation: bounce 2s infinite;
}

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

.scroll-indicator .arrow {
  width: 24px;
  height: 24px;
  border-right: 2px solid var(--text-muted);
  border-bottom: 2px solid var(--text-muted);
  transform: rotate(45deg);
}

/* ========== Skills Section ========== */
.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(120px, 1fr));
  gap: 16px;
  max-width: 700px;
  margin: 0 auto;
}

.skill-tag {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 10px 18px;
  background: var(--tag-bg);
  color: var(--tag-color);
  border-radius: 24px;
  font-size: 0.9rem;
  font-weight: 500;
  transition: all var(--transition);
  justify-content: center;
}

.skill-tag:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 12px var(--accent-light);
}

.skill-tag svg {
  width: 18px;
  height: 18px;
}

/* ========== Projects Section ========== */
.projects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 24px;
}

.project-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px;
  transition: all var(--transition);
  box-shadow: var(--shadow);
}

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

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

.project-card h3 {
  font-size: 1.15rem;
  margin-bottom: 8px;
}

.project-card p {
  color: var(--text-secondary);
  font-size: 0.9rem;
  margin-bottom: 16px;
}

.project-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 16px;
}

.project-tags span {
  font-size: 0.78rem;
  padding: 4px 12px;
  background: var(--tag-bg);
  color: var(--tag-color);
  border-radius: 16px;
}

.project-link {
  font-size: 0.9rem;
  font-weight: 600;
  display: inline-flex;
  align-items: center;
  gap: 4px;
}

/* ========== Contact Section ========== */
.contact-form {
  max-width: 520px;
  margin: 0 auto;
}

.form-group {
  margin-bottom: 20px;
}

.form-group label {
  display: block;
  font-size: 0.9rem;
  font-weight: 500;
  margin-bottom: 6px;
  color: var(--text-secondary);
}

.form-group input,
.form-group textarea {
  width: 100%;
  padding: 12px 16px;
  background: var(--input-bg);
  border: 1px solid var(--input-border);
  border-radius: var(--radius-sm);
  color: var(--text-primary);
  font-size: 0.95rem;
  font-family: inherit;
  transition: border-color var(--transition), box-shadow var(--transition);
}

.form-group input:focus,
.form-group textarea:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-light);
}

.form-group textarea {
  min-height: 120px;
  resize: vertical;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 28px;
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: var(--radius-sm);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition);
}

.btn:hover {
  background: var(--accent-hover);
  transform: translateY(-2px);
  box-shadow: 0 4px 16px var(--accent-light);
}

.btn-outline {
  background: transparent;
  color: var(--accent);
  border: 2px solid var(--accent);
}

.btn-outline:hover {
  background: var(--accent);
  color: #fff;
}

/* ========== Footer ========== */
.footer {
  border-top: 1px solid var(--border);
  padding: 32px 0;
  text-align: center;
  color: var(--text-muted);
  font-size: 0.85rem;
}

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

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

/* ========== Page Header (for subpages) ========== */
.page-header {
  padding: 140px 0 60px;
  text-align: center;
}

.page-header h1 {
  font-size: 2.4rem;
  font-weight: 800;
}

.page-header p {
  color: var(--text-secondary);
  margin-top: 8px;
}

/* ========== About Page ========== */
.about-content {
  display: grid;
  grid-template-columns: 1fr 2fr;
  gap: 48px;
  align-items: start;
  margin-bottom: 60px;
}

.about-avatar {
  width: 100%;
  max-width: 280px;
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

.about-text h2 {
  font-size: 1.6rem;
  margin-bottom: 16px;
}

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

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

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

.timeline-item {
  position: relative;
  padding-bottom: 36px;
}

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

.timeline-item::before {
  content: '';
  position: absolute;
  left: -38px;
  top: 6px;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--accent);
  border: 3px solid var(--bg-primary);
  transition: background var(--transition), border-color var(--transition);
}

.timeline-date {
  font-size: 0.85rem;
  color: var(--accent);
  font-weight: 600;
  margin-bottom: 4px;
}

.timeline-title {
  font-size: 1.1rem;
  font-weight: 600;
  margin-bottom: 4px;
}

.timeline-org {
  color: var(--text-secondary);
  font-size: 0.9rem;
}

/* ========== Blog Page ========== */
.blog-grid {
  display: grid;
  gap: 24px;
  max-width: 700px;
  margin: 0 auto;
}

.blog-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px;
  transition: all var(--transition);
  box-shadow: var(--shadow);
}

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

.blog-card .blog-date {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 8px;
}

.blog-card h2 {
  font-size: 1.3rem;
  margin-bottom: 10px;
}

.blog-card h2 a {
  color: var(--text-primary);
}

.blog-card h2 a:hover {
  color: var(--accent);
}

.blog-card .blog-excerpt {
  color: var(--text-secondary);
  font-size: 0.95rem;
  margin-bottom: 16px;
}

.blog-card .read-more {
  font-size: 0.9rem;
  font-weight: 600;
}

/* Blog post content */
.blog-post {
  max-width: 700px;
  margin: 0 auto;
  padding-bottom: 60px;
}

.blog-post .post-header {
  margin-bottom: 40px;
}

.blog-post .post-date {
  color: var(--text-muted);
  font-size: 0.9rem;
  margin-bottom: 8px;
}

.blog-post h1 {
  font-size: 2rem;
  font-weight: 800;
  margin-bottom: 12px;
  line-height: 1.3;
}

.blog-post .post-content h2 {
  font-size: 1.5rem;
  margin: 32px 0 12px;
}

.blog-post .post-content h3 {
  font-size: 1.2rem;
  margin: 24px 0 10px;
}

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

.blog-post .post-content ul,
.blog-post .post-content ol {
  color: var(--text-secondary);
  margin-bottom: 16px;
  padding-left: 24px;
}

.blog-post .post-content li {
  margin-bottom: 6px;
}

.blog-post .post-content code {
  background: var(--code-bg);
  padding: 2px 8px;
  border-radius: 4px;
  font-size: 0.9em;
  font-family: 'SF Mono', 'Fira Code', 'Fira Mono', Menlo, monospace;
}

.blog-post .post-content pre {
  background: var(--code-bg);
  padding: 20px;
  border-radius: var(--radius-sm);
  overflow-x: auto;
  margin-bottom: 20px;
}

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

.blog-post .post-content blockquote {
  border-left: 3px solid var(--accent);
  padding-left: 20px;
  margin: 20px 0;
  color: var(--text-secondary);
  font-style: italic;
}

.post-nav {
  margin-top: 48px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
  display: flex;
  justify-content: space-between;
}

/* ========== 404 Page ========== */
.error-page {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
}

.error-page h1 {
  font-size: 6rem;
  font-weight: 800;
  color: var(--accent);
  line-height: 1;
}

.error-page p {
  color: var(--text-secondary);
  margin: 16px 0 32px;
  font-size: 1.1rem;
}

/* ========== Mobile Styles ========== */
@media (max-width: 768px) {
  .hamburger {
    display: flex;
  }

  .nav-links {
    position: fixed;
    top: 64px;
    left: 0;
    right: 0;
    background: var(--nav-bg);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    flex-direction: column;
    padding: 24px;
    gap: 20px;
    transform: translateY(-100%);
    opacity: 0;
    pointer-events: none;
    transition: all var(--transition);
    border-bottom: 1px solid var(--border);
  }

  .nav-links.open {
    transform: translateY(0);
    opacity: 1;
    pointer-events: all;
  }

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

  .hero h1 {
    font-size: 2rem;
  }

  .hero-avatar {
    width: 110px;
    height: 110px;
  }

  .section {
    padding: 60px 0;
  }

  .about-content {
    grid-template-columns: 1fr;
    text-align: center;
  }

  .about-avatar {
    max-width: 200px;
    margin: 0 auto;
  }

  .page-header {
    padding: 110px 0 40px;
  }

  .page-header h1 {
    font-size: 1.8rem;
  }

  .blog-post h1 {
    font-size: 1.6rem;
  }

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

  .skills-grid {
    grid-template-columns: repeat(auto-fill, minmax(100px, 1fr));
  }

  .post-nav {
    flex-direction: column;
    gap: 12px;
  }
}

@media (max-width: 480px) {
  .container {
    padding: 0 16px;
  }

  .hero h1 {
    font-size: 1.7rem;
  }

  .section-title {
    font-size: 1.4rem;
  }

  .skills-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}