:root {
  /* Default Dark Theme Variables */
  --bg-color: #0b0c10;
  --bg-secondary: #1f2833;
  --bg-darker: #050608;
  --text-primary: #c5c6c7;
  --text-secondary: #8c92ac;
  --heading-color: #ffffff;
  --accent-color: #66fcf1; /* Cyan/Electric Blue */
  --accent-hover: #45a29e;
  --border-color: rgba(255,255,255,0.05);
  --border-color-hover: rgba(102, 252, 241, 0.2);
  --navbar-bg: rgba(11, 12, 16, 0.95);
  --hero-gradient: radial-gradient(circle at top right, rgba(102, 252, 241, 0.1), transparent 40%),
                   radial-gradient(circle at bottom left, rgba(69, 162, 158, 0.1), transparent 40%);
  --shadow: 0 10px 20px rgba(0,0,0,0.3);
  --skill-tag-bg: rgba(102, 252, 241, 0.1);
  --timeline-line: rgba(255,255,255,0.1);
  
  --font-main: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-cn: 'Noto Sans SC', sans-serif;
  --transition: all 0.3s ease;
}

/* Light Theme Variables */
[data-theme="light"] {
  --bg-color: #f0f2f5;
  --bg-secondary: #ffffff;
  --bg-darker: #e4e6eb;
  --text-primary: #4b5563;
  --text-secondary: #64748b;
  --heading-color: #1a202c;
  --accent-color: #0d9488; /* Teal-600 */
  --accent-hover: #0f766e;
  --border-color: rgba(0,0,0,0.1);
  --border-color-hover: rgba(13, 148, 136, 0.2);
  --navbar-bg: rgba(240, 242, 245, 0.95);
  --hero-gradient: radial-gradient(circle at top right, rgba(13, 148, 136, 0.1), transparent 40%),
                   radial-gradient(circle at bottom left, rgba(15, 118, 110, 0.1), transparent 40%);
  --shadow: 0 10px 20px rgba(0,0,0,0.05);
  --skill-tag-bg: rgba(13, 148, 136, 0.1);
  --timeline-line: rgba(0,0,0,0.1);
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: var(--font-cn), var(--font-main);
  background-color: var(--bg-color);
  color: var(--text-primary);
  line-height: 1.6;
  overflow-x: hidden;
  transition: background-color 0.3s ease, color 0.3s ease;
}

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

ul {
  list-style: none;
}

/* Utilities */
.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 20px;
}

.section {
  padding: 80px 0;
}

.bg-darker {
  background-color: var(--bg-darker);
  transition: background-color 0.3s ease;
}

.text-center {
  text-align: center;
}

/* Typography */
h1, h2, h3 {
  color: var(--heading-color);
  line-height: 1.2;
  transition: color 0.3s ease;
}

.section-title {
  font-size: 2.5rem;
  margin-bottom: 1rem;
  position: relative;
  display: inline-block;
  margin-bottom: 40px;
}

.section-title::after {
  content: '';
  display: block;
  width: 60px;
  height: 4px;
  background-color: var(--accent-color);
  margin-top: 10px;
  border-radius: 2px;
}

.section-subtitle {
  margin-top: -30px;
  margin-bottom: 50px;
  color: var(--text-secondary);
}

/* Buttons */
.btn {
  display: inline-block;
  padding: 12px 30px;
  border-radius: 5px;
  font-weight: 600;
  cursor: pointer;
  font-size: 1rem;
  transition: var(--transition);
}

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

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

.btn-outline {
  background-color: transparent;
  color: var(--heading-color);
  border: 2px solid var(--heading-color);
  margin-left: 15px;
}

.btn-outline:hover {
  background-color: var(--heading-color);
  color: var(--bg-color);
}

/* Navbar */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  background-color: var(--navbar-bg);
  backdrop-filter: blur(10px);
  z-index: 1000;
  padding: 20px 0;
  border-bottom: 1px solid var(--border-color);
  transition: background-color 0.3s ease, border-bottom 0.3s ease;
}

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

.nav-controls {
  display: flex;
  align-items: center;
  gap: 30px;
}

.logo {
  font-size: 1.8rem;
  font-weight: 800;
  color: var(--heading-color);
  font-family: var(--font-main);
}

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

.nav-links {
  display: flex;
  gap: 30px;
}

.nav-links a {
  font-weight: 500;
  font-size: 1rem;
  color: var(--text-primary);
}

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

/* Theme Toggle Button */
.theme-toggle {
  background: transparent;
  border: none;
  cursor: pointer;
  color: var(--heading-color);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 5px;
  border-radius: 50%;
  transition: var(--transition);
}

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

.theme-toggle svg {
  width: 24px;
  height: 24px;
  fill: none;
  stroke: currentColor;
  stroke-width: 2;
  stroke-linecap: round;
  stroke-linejoin: round;
}

/* Hamburger */
.hamburger {
  display: none;
  cursor: pointer;
  z-index: 1001;
}

.hamburger span {
  display: block;
  width: 25px;
  height: 3px;
  background-color: var(--heading-color);
  margin: 5px 0;
  transition: all 0.3s ease;
}

/* Hero Section */
.hero {
  height: 100vh;
  display: flex;
  align-items: center;
  position: relative;
  background: var(--hero-gradient);
  transition: background 0.3s ease;
}

.hero-content {
  width: 100%;
}

.greeting {
  font-size: 1.2rem;
  color: var(--accent-color);
  margin-bottom: 15px;
  font-weight: 600;
}

.headline {
  font-size: 4rem;
  margin-bottom: 20px;
  font-weight: 800;
}

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

.sub-headline {
  font-size: 1.5rem;
  color: var(--text-secondary);
  margin-bottom: 40px;
  max-width: 600px;
}

.scroll-down {
  position: absolute;
  bottom: 30px;
  left: 50%;
  transform: translateX(-50%);
  animation: bounce 2s infinite;
  color: var(--text-secondary);
  font-size: 1.5rem;
}

@keyframes bounce {
  0%, 20%, 50%, 80%, 100% {transform: translateX(-50%) translateY(0);}
  40% {transform: translateX(-50%) translateY(-10px);}
  60% {transform: translateX(-50%) translateY(-5px);}
}

/* About Section */
.about-grid {
  display: grid;
  grid-template-columns: 3fr 2fr;
  gap: 50px;
  align-items: center;
}

.about-text p {
  margin-bottom: 20px;
  font-size: 1.1rem;
}

.about-stats {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
}

.stat-item {
  background-color: var(--bg-secondary);
  padding: 30px;
  border-radius: 10px;
  text-align: center;
  transition: transform 0.3s, background-color 0.3s;
  box-shadow: 0 4px 6px rgba(0,0,0,0.02);
}

.stat-item:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow);
}

.stat-number {
  display: block;
  font-size: 2.5rem;
  font-weight: 800;
  color: var(--accent-color);
  margin-bottom: 5px;
}

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

/* Skills Section */
.skills-wrapper {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 30px;
}

.skill-category {
  background: var(--bg-secondary);
  padding: 30px;
  border-radius: 12px;
  border: 1px solid var(--border-color);
  transition: background-color 0.3s;
}

.skill-category h3 {
  margin-bottom: 20px;
  font-size: 1.2rem;
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 10px;
  display: inline-block;
}

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

.tags span {
  background-color: var(--skill-tag-bg);
  color: var(--accent-color);
  padding: 8px 15px;
  border-radius: 20px;
  font-size: 0.9rem;
  border: 1px solid var(--border-color-hover);
  transition: var(--transition);
}

.tags span:hover {
  background-color: var(--accent-color);
  color: var(--bg-color);
}

/* Experience Section - Vertical Timeline */
.timeline {
  position: relative;
  max-width: 800px;
  margin: 0 auto;
}

.timeline::after {
  content: '';
  position: absolute;
  width: 2px;
  background-color: var(--timeline-line);
  top: 0;
  bottom: 0;
  left: 20px;
}

.timeline-item {
  padding: 10px 40px;
  position: relative;
  margin-bottom: 40px;
  width: 100%;
}

.timeline-item::after {
  content: '';
  position: absolute;
  width: 16px;
  height: 16px;
  right: auto;
  left: 13px;
  background-color: var(--bg-color);
  border: 3px solid var(--accent-color);
  top: 15px;
  border-radius: 50%;
  z-index: 1;
  transition: background-color 0.3s;
}

.timeline-content {
  padding: 25px;
  background-color: var(--bg-secondary);
  border-radius: 8px;
  position: relative;
  transition: var(--transition);
  border-left: 3px solid transparent;
  box-shadow: 0 4px 6px rgba(0,0,0,0.02);
}

.timeline-content:hover {
  border-left: 3px solid var(--accent-color);
  transform: translateX(5px);
  box-shadow: var(--shadow);
}

.timeline-date {
  font-size: 0.85rem;
  color: var(--accent-color);
  margin-bottom: 8px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1px;
}

.timeline-content h3 {
  font-size: 1.3rem;
  margin-bottom: 5px;
}

.timeline-content .role {
  font-style: italic;
  color: var(--text-secondary);
  margin-bottom: 10px;
  font-weight: 500;
}

/* Contact Section */
.big-btn {
  font-size: 1.2rem;
  padding: 15px 40px;
  margin: 30px 0;
}

.social-links {
  display: flex;
  justify-content: center;
  gap: 20px;
  margin-top: 30px;
  color: var(--text-secondary);
}

.social-links a,
.social-links span {
  cursor: pointer;
  transition: color 0.3s;
  color: var(--text-secondary);
  font-size: 1.1rem;
}

.social-links a:hover,
.social-links span:hover {
  color: var(--accent-color);
}

/* Footer */
footer {
  padding: 30px 0;
  text-align: center;
  color: var(--text-secondary);
  font-size: 0.9rem;
  border-top: 1px solid var(--border-color);
}

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

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

/* Responsive */
@media (max-width: 768px) {
  .headline {
    font-size: 2.5rem;
  }
  
  .sub-headline {
    font-size: 1.2rem;
  }

  .about-grid {
    grid-template-columns: 1fr;
  }
  
  .hamburger {
    display: block;
  }
  
  /* Adjusted mobile nav for toggle support */
  .nav-controls {
    gap: 15px;
  }

  .nav-links {
    position: absolute;
    top: 0;
    right: 0;
    height: 100vh;
    width: 70%;
    background-color: var(--bg-secondary);
    flex-direction: column;
    align-items: center;
    justify-content: center;
    transform: translateX(100%);
    transition: transform 0.3s ease-in-out;
    box-shadow: -5px 0 15px rgba(0,0,0,0.5);
    z-index: 999; /* Below hamburger/toggle if needed, but hamburger z-index is 1001 */
  }

  .nav-links.active {
    transform: translateX(0%);
  }
  
  .timeline::after {
    left: 20px;
  }
  
  .timeline-item {
    padding-left: 50px;
    padding-right: 0;
  }
  
  .timeline-item::after {
    left: 13px;
  }

  .btn-outline {
    margin-left: 0;
    margin-top: 15px;
    display: inline-block;
  }
}