/* ===========================
   CSS Variables & Reset
   =========================== */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  /* Light Mode Colors */
  --primary-color: #3b82f6;
  --primary-hover: #2563eb;
  --secondary-color: #8b5cf6;
  --text-primary: #1f2937;
  --text-secondary: #6b7280;
  --bg-primary: #ffffff;
  --bg-secondary: #f9fafb;
  --bg-tertiary: #f3f4f6;
  --border-color: #e5e7eb;
  --shadow: rgba(0, 0, 0, 0.1);
  --shadow-lg: rgba(0, 0, 0, 0.15);
  
  /* Spacing */
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 1.5rem;
  --spacing-lg: 2rem;
  --spacing-xl: 3rem;
  --spacing-2xl: 4rem;
  
  /* Border Radius */
  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  
  /* Transitions */
  --transition: all 0.3s ease;
}

body.dark-mode {
  --text-primary: #f9fafb;
  --text-secondary: #d1d5db;
  --bg-primary: #111827;
  --bg-secondary: #1f2937;
  --bg-tertiary: #374151;
  --border-color: #4b5563;
  --shadow: rgba(0, 0, 0, 0.3);
  --shadow-lg: rgba(0, 0, 0, 0.5);
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen',
    'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue',
    sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  color: var(--text-primary);
  background-color: var(--bg-primary);
  line-height: 1.6;
  transition: background-color 0.3s ease, color 0.3s ease;
}

.portfolio {
  min-height: 100vh;
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-md);
}

/* ===========================
   Navigation Bar
   =========================== */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  background-color: var(--bg-primary);
  border-bottom: 1px solid var(--border-color);
  padding: var(--spacing-sm) 0;
  z-index: 1000;
  box-shadow: 0 2px 8px var(--shadow);
  transition: var(--transition);
}

.nav-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-md);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav-logo {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--primary-color);
}

.nav-menu {
  display: flex;
  list-style: none;
  gap: var(--spacing-md);
  align-items: center;
}

.nav-menu li a {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  color: var(--text-primary);
  text-decoration: none;
  padding: var(--spacing-xs) var(--spacing-sm);
  border-radius: var(--radius-md);
  transition: var(--transition);
  cursor: pointer;
  font-weight: 500;
}

.nav-menu li a:hover {
  background-color: var(--bg-tertiary);
  color: var(--primary-color);
}

.nav-toggle {
  display: none;
  background: none;
  border: none;
  color: var(--text-primary);
  cursor: pointer;
  padding: var(--spacing-xs);
  font-size: 1.5rem;
}

.theme-toggle {
  background-color: var(--bg-tertiary);
  border: none;
  padding: var(--spacing-xs) var(--spacing-sm);
  border-radius: var(--radius-md);
  cursor: pointer;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: var(--transition);
  font-size: 1.2rem;
}

.theme-toggle:hover {
  background-color: var(--primary-color);
  color: white;
}

/* ===========================
   Sections
   =========================== */
.section {
  padding: var(--spacing-2xl) 0;
  min-height: 100vh;
  display: flex;
  align-items: center;
}

.section-title {
  font-size: 2.5rem;
  font-weight: 700;
  text-align: center;
  margin-bottom: var(--spacing-xl);
  color: var(--text-primary);
  position: relative;
  padding-bottom: 20px;
}

.section-title::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 80px;
  height: 4px;
  background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
  border-radius: 2px;
}

/* ===========================
   Home Section
   =========================== */
.home-section {
  margin-top: 60px;
  background: linear-gradient(135deg, var(--bg-secondary) 0%, var(--bg-primary) 100%);
}

.home-content {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--spacing-xl);
  align-items: center;
}

.home-text {
  animation: fadeInLeft 1s ease-out;
}

.home-title {
  font-size: 3rem;
  font-weight: 800;
  margin-bottom: var(--spacing-sm);
  line-height: 1.2;
}

.highlight {
  background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.home-subtitle {
  font-size: 1.5rem;
  color: var(--text-secondary);
  margin-bottom: var(--spacing-md);
}

.home-description {
  font-size: 1.1rem;
  color: var(--text-secondary);
  margin-bottom: var(--spacing-lg);
  line-height: 1.8;
}

.social-links {
  display: flex;
  gap: var(--spacing-sm);
  margin-bottom: var(--spacing-lg);
}

.social-icon {
  width: 50px;
  height: 50px;
  display: flex;
  align-items: center;
  justify-content: center;
  background-color: var(--bg-tertiary);
  border-radius: 50%;
  color: var(--text-primary);
  text-decoration: none;
  transition: var(--transition);
  font-size: 1.5rem;
}

.social-icon:hover {
  background-color: var(--primary-color);
  color: white;
  transform: translateY(-5px);
}

.home-image {
  display: flex;
  justify-content: center;
  align-items: center;
  animation: fadeInRight 1s ease-out;
}

.image-placeholder {
  width: 400px;
  height: 400px;
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  box-shadow: 0 20px 40px var(--shadow-lg);
  font-size: 120px;
}

/* ===========================
   Buttons
   =========================== */
.btn-primary {
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-xs);
  background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
  color: white;
  padding: var(--spacing-sm) var(--spacing-lg);
  border: none;
  border-radius: var(--radius-md);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
  box-shadow: 0 4px 12px var(--shadow);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 16px var(--shadow-lg);
}

/* ===========================
   About Section
   =========================== */
.about-section {
  background-color: var(--bg-primary);
}

.about-content {
  max-width: 800px;
  margin: 0 auto;
}

.about-text {
  font-size: 1.1rem;
  color: var(--text-secondary);
  margin-bottom: var(--spacing-md);
  text-align: center;
  line-height: 1.8;
}

.skills {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-sm);
  justify-content: center;
  margin-top: var(--spacing-lg);
}

.skill-tag {
  background-color: var(--bg-tertiary);
  color: var(--text-primary);
  padding: var(--spacing-xs) var(--spacing-md);
  border-radius: var(--radius-lg);
  font-weight: 600;
  transition: var(--transition);
}

.skill-tag:hover {
  background-color: var(--primary-color);
  color: white;
  transform: translateY(-3px);
}

/* ===========================
   Education Section
   =========================== */
.education-section {
  background-color: var(--bg-secondary);
}

.timeline {
  max-width: 800px;
  margin: 0 auto;
  position: relative;
}

.timeline::before {
  content: '';
  position: absolute;
  left: 50%;
  transform: translateX(-50%);
  width: 2px;
  height: 100%;
  background: linear-gradient(180deg, var(--primary-color), var(--secondary-color));
}

.timeline-item {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-xl);
  position: relative;
}

.timeline-item:nth-child(odd) .timeline-content {
  grid-column: 1;
  text-align: right;
}

.timeline-item:nth-child(even) .timeline-content {
  grid-column: 3;
  text-align: left;
}

.timeline-icon {
  grid-column: 2;
  width: 60px;
  height: 60px;
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  z-index: 1;
  font-size: 1.5rem;
}

.timeline-content {
  background-color: var(--bg-primary);
  padding: var(--spacing-md);
  border-radius: var(--radius-lg);
  box-shadow: 0 4px 12px var(--shadow);
}

.timeline-content h3 {
  font-size: 1.3rem;
  margin-bottom: var(--spacing-xs);
  color: var(--text-primary);
}

.timeline-date {
  color: var(--primary-color);
  font-weight: 600;
  margin-bottom: var(--spacing-xs);
}

.timeline-location {
  color: var(--text-secondary);
  font-weight: 600;
  margin-bottom: var(--spacing-xs);
}

.timeline-description {
  color: var(--text-secondary);
  line-height: 1.6;
}

/* ===========================
   Projects Section
   =========================== */
.projects-section {
  background-color: var(--bg-primary);
}

.projects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--spacing-lg);
}

.project-card {
  background-color: var(--bg-secondary);
  padding: var(--spacing-lg);
  border-radius: var(--radius-xl);
  box-shadow: 0 4px 12px var(--shadow);
  transition: var(--transition);
  border: 1px solid var(--border-color);
}

.project-card:hover {
  transform: translateY(-8px);
  box-shadow: 0 8px 24px var(--shadow-lg);
}

.project-header {
  width: 70px;
  height: 70px;
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  margin-bottom: var(--spacing-md);
  font-size: 2rem;
}

.project-card h3 {
  font-size: 1.3rem;
  margin-bottom: var(--spacing-sm);
  color: var(--text-primary);
}

.project-card p {
  color: var(--text-secondary);
  line-height: 1.6;
  margin-bottom: var(--spacing-md);
}

.project-tags {
  display: flex;
  gap: var(--spacing-xs);
  flex-wrap: wrap;
}

.project-tags span {
  background-color: var(--bg-tertiary);
  color: var(--text-primary);
  padding: 0.25rem 0.75rem;
  border-radius: var(--radius-md);
  font-size: 0.875rem;
  font-weight: 500;
}

/* ===========================
   Achievements Section
   =========================== */
.achievements-section {
  background-color: var(--bg-secondary);
}

.achievements-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--spacing-lg);
}

.achievement-card {
  background-color: var(--bg-primary);
  padding: var(--spacing-lg);
  border-radius: var(--radius-xl);
  text-align: center;
  box-shadow: 0 4px 12px var(--shadow);
  transition: var(--transition);
  border: 1px solid var(--border-color);
}

.achievement-card:hover {
  transform: translateY(-8px);
  box-shadow: 0 8px 24px var(--shadow-lg);
}

.achievement-icon {
  color: var(--primary-color);
  margin-bottom: var(--spacing-md);
  font-size: 3rem;
}

.achievement-card h3 {
  font-size: 1.2rem;
  margin-bottom: var(--spacing-sm);
  color: var(--text-primary);
}

.achievement-card p {
  color: var(--text-secondary);
  line-height: 1.6;
}

/* ===========================
   Hobbies Section
   =========================== */
.hobbies-section {
  background-color: var(--bg-primary);
}

.hobbies-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--spacing-lg);
}

.hobby-card {
  background-color: var(--bg-secondary);
  padding: var(--spacing-lg);
  border-radius: var(--radius-xl);
  text-align: center;
  box-shadow: 0 4px 12px var(--shadow);
  transition: var(--transition);
  border: 1px solid var(--border-color);
}

.hobby-card:hover {
  transform: translateY(-8px);
  box-shadow: 0 8px 24px var(--shadow-lg);
}

.hobby-card i {
  color: var(--secondary-color);
  margin-bottom: var(--spacing-md);
  font-size: 2.5rem;
}

.hobby-card h3 {
  font-size: 1.2rem;
  margin-bottom: var(--spacing-sm);
  color: var(--text-primary);
}

.hobby-card p {
  color: var(--text-secondary);
  line-height: 1.6;
}

/* ===========================
   Publications Section
   =========================== */
.publications-section {
  background-color: var(--bg-secondary);
}

.publications-list {
  max-width: 900px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: var(--spacing-lg);
}

.publication-item {
  background-color: var(--bg-primary);
  padding: var(--spacing-lg);
  border-radius: var(--radius-lg);
  display: flex;
  gap: var(--spacing-md);
  box-shadow: 0 4px 12px var(--shadow);
  transition: var(--transition);
  border: 1px solid var(--border-color);
}

.publication-item:hover {
  transform: translateX(8px);
  box-shadow: 0 6px 16px var(--shadow-lg);
}

.publication-icon {
  color: var(--primary-color);
  flex-shrink: 0;
  font-size: 2rem;
}

.publication-content h3 {
  font-size: 1.3rem;
  margin-bottom: var(--spacing-xs);
  color: var(--text-primary);
}

.publication-meta {
  color: var(--secondary-color);
  font-size: 0.9rem;
  font-weight: 600;
  margin-bottom: var(--spacing-xs);
}

.publication-content p {
  color: var(--text-secondary);
  line-height: 1.6;
}

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

.contact-content {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--spacing-xl);
  max-width: 1000px;
  margin: 0 auto;
}

.contact-info h3 {
  font-size: 1.8rem;
  margin-bottom: var(--spacing-md);
  color: var(--text-primary);
}

.contact-info p {
  color: var(--text-secondary);
  font-size: 1.1rem;
  margin-bottom: var(--spacing-lg);
  line-height: 1.6;
}

.contact-details {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
}

.contact-detail {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  color: var(--text-secondary);
  font-size: 1rem;
}

.contact-detail i {
  color: var(--primary-color);
  font-size: 1.5rem;
}

.contact-form {
  background-color: var(--bg-secondary);
  padding: var(--spacing-lg);
  border-radius: var(--radius-xl);
  box-shadow: 0 4px 12px var(--shadow);
}

.form-group {
  margin-bottom: var(--spacing-md);
}

.form-group label {
  display: block;
  margin-bottom: var(--spacing-xs);
  color: var(--text-primary);
  font-weight: 600;
}

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

.form-group input:focus,
.form-group textarea:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

.form-group textarea {
  resize: vertical;
}

/* ===========================
   Footer
   =========================== */
.footer {
  background-color: var(--bg-secondary);
  padding: var(--spacing-lg) 0;
  border-top: 1px solid var(--border-color);
}

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

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

.footer-links {
  display: flex;
  gap: var(--spacing-md);
}

.footer-links a {
  color: var(--text-secondary);
  text-decoration: none;
  transition: var(--transition);
}

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

/* ===========================
   Animations
   =========================== */
@keyframes fadeInLeft {
  from {
    opacity: 0;
    transform: translateX(-50px);
  }
  to {
    opacity: 1;
    transform: translateX(0);
  }
}

@keyframes fadeInRight {
  from {
    opacity: 0;
    transform: translateX(50px);
  }
  to {
    opacity: 1;
    transform: translateX(0);
  }
}

/* ===========================
   Responsive Design - Tablet
   =========================== */
@media (max-width: 968px) {
  .section-title {
    font-size: 2rem;
  }

  .home-title {
    font-size: 2.5rem;
  }

  .home-subtitle {
    font-size: 1.3rem;
  }

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

  .home-text {
    order: 2;
  }

  .home-image {
    order: 1;
  }

  .image-placeholder {
    width: 300px;
    height: 300px;
  }

  .social-links {
    justify-content: center;
  }

  .timeline::before {
    left: 30px;
  }

  .timeline-item {
    grid-template-columns: auto 1fr;
    gap: var(--spacing-md);
  }

  .timeline-item:nth-child(odd) .timeline-content,
  .timeline-item:nth-child(even) .timeline-content {
    grid-column: 2;
    text-align: left;
  }

  .timeline-icon {
    grid-column: 1;
    grid-row: 1;
  }

  .contact-content {
    grid-template-columns: 1fr;
  }
}

/* ===========================
   Responsive Design - Mobile
   =========================== */
@media (max-width: 768px) {
  .nav-menu {
    position: fixed;
    left: -100%;
    top: 60px;
    flex-direction: column;
    background-color: var(--bg-primary);
    width: 100%;
    text-align: center;
    transition: 0.3s;
    box-shadow: 0 10px 27px var(--shadow);
    padding: var(--spacing-lg) 0;
    border-bottom: 1px solid var(--border-color);
  }

  .nav-menu.active {
    left: 0;
  }

  .nav-toggle {
    display: block;
  }

  .section {
    padding: var(--spacing-xl) 0;
    min-height: auto;
  }

  .section-title {
    font-size: 1.8rem;
  }

  .home-title {
    font-size: 2rem;
  }

  .home-subtitle {
    font-size: 1.1rem;
  }

  .home-description {
    font-size: 1rem;
  }

  .image-placeholder {
    width: 250px;
    height: 250px;
    font-size: 80px;
  }

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

  .footer .container {
    flex-direction: column;
    gap: var(--spacing-sm);
    text-align: center;
  }

  .footer-links {
    flex-direction: column;
    gap: var(--spacing-xs);
  }

  .timeline-icon {
    width: 50px;
    height: 50px;
    font-size: 1.2rem;
  }
}

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

  .section-title {
    font-size: 1.5rem;
  }

  .home-title {
    font-size: 1.5rem;
  }

  .home-subtitle {
    font-size: 1rem;
  }

  .social-icon {
    width: 40px;
    height: 40px;
    font-size: 1.2rem;
  }

  .btn-primary {
    padding: var(--spacing-xs) var(--spacing-md);
    font-size: 0.9rem;
  }
}