/* Modern color scheme */
:root {
  --primary-color: #2d3e50;
  --secondary-color: #3498db;
  --accent-color: #1abc9c;
  --text-color: #333333;
  --light-text-color: #ffffff;
  --light-color: #f5f7fa;
  --border-color: #e0e0e0;
  --card-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
  --transition-speed: 0.3s;
}

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

body {
  font-family: 'Inter', 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  line-height: 1.6;
  color: var(--text-color);
  background-color: #ffffff;
  overflow-x: hidden;
  scroll-behavior: smooth;
}

.container {
  width: 90%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 15px;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
  font-weight: 700;
  line-height: 1.3;
  margin-bottom: 1rem;
  color: var(--primary-color);
}

h1 {
  font-size: 2.5rem;
}

h2 {
  font-size: 2rem;
}

h3 {
  font-size: 1.5rem;
}

p {
  margin-bottom: 1.5rem;
}

a {
  color: var(--secondary-color);
  text-decoration: none;
  transition: color var(--transition-speed) ease;
}

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

.section-title {
  text-align: center;
  margin-bottom: 2.5rem;
  position: relative;
  padding-bottom: 1rem;
}

.section-title::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 80px;
  height: 3px;
  background-color: var(--accent-color);
}

/* Header */
header {
  background-color: var(--primary-color);
  padding: 1rem 0;
  position: sticky;
  top: 0;
  z-index: 1000;
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
  transition: all var(--transition-speed) ease;
}

header.scrolled {
  padding: 0.5rem 0;
  background-color: rgba(45, 62, 80, 0.95);
  backdrop-filter: blur(10px);
}

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

.logo a {
  color: var(--light-text-color);
  font-size: 1.5rem;
  font-weight: 700;
  transition: all var(--transition-speed) ease;
}

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

/* Navigation */
nav ul {
  display: flex;
  list-style: none;
}

nav ul li {
  margin-left: 1.5rem;
}

nav ul li a {
  color: var(--light-text-color);
  font-weight: 500;
  padding: 0.5rem 0;
  position: relative;
  transition: all var(--transition-speed) ease;
}

nav ul li a::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 2px;
  background-color: var(--accent-color);
  transition: width var(--transition-speed) ease;
}

nav ul li a:hover::after,
nav ul li a.active::after {
  width: 100%;
}

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

.hamburger {
  display: none;
  background: none;
  border: none;
  color: var(--light-text-color);
  font-size: 1.5rem;
  cursor: pointer;
}

/* Hero section */
.hero {
  background-color: var(--light-color);
  padding: 5rem 0;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: linear-gradient(135deg, rgba(52, 152, 219, 0.1) 0%, rgba(26, 188, 156, 0.1) 100%);
  z-index: 0;
}

.hero-content {
  position: relative;
  z-index: 1;
  max-width: 800px;
  margin: 0 auto;
}

.profile-image {
  width: 200px;
  height: 200px;
  border-radius: 50%;
  margin: 0 auto 2rem;
  object-fit: cover;
  border: 5px solid #fff;
  box-shadow: var(--card-shadow);
  transition: transform var(--transition-speed) ease;
}

.profile-image:hover {
  transform: scale(1.05);
}

.hero h1 {
  margin-bottom: 1rem;
  font-size: 3rem;
  color: var(--primary-color);
}

.hero p {
  font-size: 1.25rem;
  margin-bottom: 2rem;
  color: var(--text-color);
}

/* Buttons */
.btn {
  display: inline-block;
  padding: 0.75rem 1.5rem;
  background-color: var(--secondary-color);
  color: var(--light-text-color);
  border-radius: 4px;
  font-weight: 500;
  text-align: center;
  transition: all var(--transition-speed) ease;
  border: none;
  cursor: pointer;
  margin: 0.5rem;
  box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
}

.btn:hover {
  background-color: var(--accent-color);
  color: var(--light-text-color);
  transform: translateY(-2px);
  box-shadow: 0 4px 8px rgba(0, 0, 0, 0.15);
}

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

.btn-secondary:hover {
  background-color: var(--secondary-color);
}

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

.btn-outline:hover {
  background-color: var(--secondary-color);
  color: var(--light-text-color);
}

/* Grid layout */
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 2rem;
}

/* Cards */
.card {
  background-color: #fff;
  border-radius: 8px;
  padding: 2rem;
  box-shadow: var(--card-shadow);
  transition: all var(--transition-speed) ease;
  border: 1px solid var(--border-color);
  height: 100%;
}

.card:hover {
  transform: translateY(-5px);
  box-shadow: 0 8px 15px rgba(0, 0, 0, 0.1);
}

.card-title {
  color: var(--primary-color);
  margin-bottom: 1rem;
  position: relative;
  padding-bottom: 0.5rem;
}

.card-title::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 50px;
  height: 2px;
  background-color: var(--accent-color);
}

/* Timeline */
.timeline-item {
  margin-bottom: 1.5rem;
  position: relative;
  padding-left: 1.5rem;
  border-left: 2px solid var(--secondary-color);
  padding-bottom: 1rem;
}

.timeline-date {
  font-weight: 700;
  color: var(--secondary-color);
  margin-bottom: 0.25rem;
}

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

.timeline-subtitle {
  color: #666;
  font-style: italic;
  margin-bottom: 0.5rem;
}

/* Publications */
.publication {
  margin-bottom: 2rem;
  padding-bottom: 2rem;
  border-bottom: 1px solid var(--border-color);
}

.publication:last-child {
  border-bottom: none;
}

.publication-title {
  color: var(--primary-color);
  margin-bottom: 0.5rem;
}

.publication-meta {
  color: #666;
  font-style: italic;
  margin-bottom: 1rem;
}

/* Contact form */
.contact-form {
  max-width: 600px;
  margin: 0 auto;
}

.form-group {
  margin-bottom: 1.5rem;
}

label {
  display: block;
  margin-bottom: 0.5rem;
  font-weight: 500;
}

input, textarea {
  width: 100%;
  padding: 0.75rem;
  border: 1px solid var(--border-color);
  border-radius: 4px;
  font-family: inherit;
  font-size: 1rem;
  transition: border-color var(--transition-speed) ease;
}

input:focus, textarea:focus {
  outline: none;
  border-color: var(--secondary-color);
  box-shadow: 0 0 0 3px rgba(52, 152, 219, 0.2);
}

textarea {
  min-height: 150px;
  resize: vertical;
}

/* Contact info */
.contact-info {
  margin-bottom: 2rem;
}

.contact-info i {
  color: var(--secondary-color);
  margin-right: 0.5rem;
  width: 20px;
  text-align: center;
}

/* Footer */
footer {
  background-color: var(--primary-color);
  color: var(--light-text-color);
  padding: 3rem 0;
  text-align: center;
}

footer p {
  margin-bottom: 1rem;
}

.social-icons {
  display: flex;
  justify-content: center;
  list-style: none;
  margin-bottom: 1.5rem;
}

.social-icons li {
  margin: 0 0.5rem;
}

.social-icons a {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  background-color: rgba(255, 255, 255, 0.1);
  border-radius: 50%;
  color: var(--light-text-color);
  transition: all var(--transition-speed) ease;
}

.social-icons a:hover {
  background-color: var(--accent-color);
  transform: translateY(-3px);
}

.footer-links {
  display: flex;
  justify-content: center;
  list-style: none;
  flex-wrap: wrap;
}

.footer-links li {
  margin: 0 1rem;
}

.footer-links a {
  color: var(--light-text-color);
  transition: color var(--transition-speed) ease;
}

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

/* Utility classes */
.text-center {
  text-align: center;
}

.mb-2 {
  margin-bottom: 2rem;
}

.mt-2 {
  margin-top: 2rem;
}

/* Animations */
@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.animate-fade-in {
  animation: fadeIn 0.8s ease forwards;
}

section {
  padding: 5rem 0;
  position: relative;
}

section:nth-child(even) {
  background-color: var(--light-color);
}

/* Skill bars */
.skill-bar {
  margin-bottom: 1.5rem;
}

.skill-name {
  display: flex;
  justify-content: space-between;
  margin-bottom: 0.5rem;
}

.skill-level {
  height: 10px;
  background-color: #e0e0e0;
  border-radius: 5px;
  overflow: hidden;
}

.skill-percent {
  height: 100%;
  background-color: var(--secondary-color);
  border-radius: 5px;
  transition: width 1s ease;
}

/* Research interests */
.interest-icon {
  font-size: 2.5rem;
  color: var(--accent-color);
  margin-bottom: 1rem;
}

/* Back to top button */
.back-to-top {
  position: fixed;
  bottom: 20px;
  right: 20px;
  width: 40px;
  height: 40px;
  background-color: var(--secondary-color);
  color: var(--light-text-color);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transition: all var(--transition-speed) ease;
  z-index: 999;
}

.back-to-top.visible {
  opacity: 1;
  visibility: visible;
}

.back-to-top:hover {
  background-color: var(--accent-color);
  transform: translateY(-3px);
}

/* Theme toggle */
.theme-toggle {
  position: fixed;
  top: 100px;
  right: 20px;
  width: 40px;
  height: 40px;
  background-color: var(--secondary-color);
  color: var(--light-text-color);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  z-index: 999;
  transition: all var(--transition-speed) ease;
}

.theme-toggle:hover {
  background-color: var(--accent-color);
  transform: translateY(-3px);
}

/* Dark theme */
body.dark-theme {
  --primary-color: #1a2530;
  --secondary-color: #2980b9;
  --accent-color: #16a085;
  --text-color: #e0e0e0;
  --light-text-color: #ffffff;
  --light-color: #2c3e50;
  --border-color: #34495e;
  background-color: #121212;
}

body.dark-theme .card,
body.dark-theme input,
body.dark-theme textarea {
  background-color: #1e272e;
  color: var(--text-color);
}

body.dark-theme .hero {
  background-color: #1a2530;
}

/* Scroll reveal */
.reveal {
  opacity: 0;
  transform: translateY(30px);
  transition: all 0.8s ease;
}

.reveal.active {
  opacity: 1;
  transform: translateY(0);
}

/* Tooltip */
.tooltip {
  position: relative;
  display: inline-block;
}

.tooltip .tooltip-text {
  visibility: hidden;
  width: 120px;
  background-color: var(--primary-color);
  color: var(--light-text-color);
  text-align: center;
  border-radius: 4px;
  padding: 5px;
  position: absolute;
  z-index: 1;
  bottom: 125%;
  left: 50%;
  transform: translateX(-50%);
  opacity: 0;
  transition: opacity var(--transition-speed) ease;
}

.tooltip:hover .tooltip-text {
  visibility: visible;
  opacity: 1;
}

/* Progress indicator */
.progress-container {
  position: fixed;
  top: 0;
  width: 100%;
  height: 4px;
  z-index: 1001;
}

.progress-bar {
  height: 4px;
  background-color: var(--accent-color);
  width: 0%;
}

/* Loader */
.loader {
  display: flex;
  justify-content: center;
  align-items: center;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: #fff;
  z-index: 9999;
  transition: opacity 0.5s ease, visibility 0.5s ease;
}

.loader.hidden {
  opacity: 0;
  visibility: hidden;
}

.loader-spinner {
  width: 50px;
  height: 50px;
  border: 5px solid var(--light-color);
  border-top: 5px solid var(--secondary-color);
  border-radius: 50%;
  animation: spin 1s linear infinite;
}

@keyframes spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}

/* Hover effects */
.hover-lift {
  transition: transform var(--transition-speed) ease;
}

.hover-lift:hover {
  transform: translateY(-5px);
}

/* Image gallery */
.gallery {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
  gap: 1rem;
}

.gallery-item {
  overflow: hidden;
  border-radius: 8px;
  position: relative;
}

.gallery-item img {
  width: 100%;
  height: 200px;
  object-fit: cover;
  transition: transform var(--transition-speed) ease;
}

.gallery-item:hover img {
  transform: scale(1.1);
}

.gallery-caption {
  position: absolute;
  bottom: 0;
  left: 0;
  width: 100%;
  background-color: rgba(0, 0, 0, 0.7);
  color: #fff;
  padding: 0.5rem;
  transform: translateY(100%);
  transition: transform var(--transition-speed) ease;
}

.gallery-item:hover .gallery-caption {
  transform: translateY(0);
}

/* Scroll indicator */
.scroll-indicator {
  position: absolute;
  bottom: 30px;
  left: 50%;
  transform: translateX(-50%);
  display: flex;
  flex-direction: column;
  align-items: center;
  color: var(--primary-color);
  animation: bounce 2s infinite;
}

.scroll-indicator i {
  font-size: 2rem;
}

.scroll-indicator span {
  font-size: 0.8rem;
  margin-top: 0.5rem;
}

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

/* Tabs */
.tabs {
  display: flex;
  flex-wrap: wrap;
  margin-bottom: 2rem;
}

.tab-link {
  padding: 0.75rem 1.5rem;
  background-color: #f5f5f5;
  color: var(--text-color);
  cursor: pointer;
  border: none;
  outline: none;
  transition: all var(--transition-speed) ease;
}

.tab-link:hover {
  background-color: #e0e0e0;
}

.tab-link.active {
  background-color: var(--secondary-color);
  color: var(--light-text-color);
}

.tab-content {
  display: none;
  padding: 2rem;
  border: 1px solid #e0e0e0;
  border-top: none;
}

.tab-content.active {
  display: block;
  animation: fadeIn 0.5s ease;
}

/* Accordion */
.accordion {
  margin-bottom: 1rem;
}

.accordion-header {
  padding: 1rem;
  background-color: #f5f5f5;
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  transition: background-color var(--transition-speed) ease;
}

.accordion-header:hover {
  background-color: #e0e0e0;
}

.accordion-content {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease;
}

.accordion.active .accordion-content {
  max-height: 500px;
}

.accordion-icon {
  transition: transform var(--transition-speed) ease;
}

.accordion.active .accordion-icon {
  transform: rotate(180deg);
}

/* Testimonials */
.testimonial {
  text-align: center;
  padding: 2rem;
  background-color: #fff;
  border-radius: 8px;
  box-shadow: var(--card-shadow);
}

.testimonial-text {
  font-style: italic;
  margin-bottom: 1.5rem;
}

.testimonial-author {
  font-weight: 700;
}

.testimonial-position {
  color: #666;
  font-size: 0.9rem;
}

/* Counter */
.counter {
  text-align: center;
}

.counter-number {
  font-size: 3rem;
  font-weight: 700;
  color: var(--secondary-color);
  margin-bottom: 0.5rem;
}

.counter-title {
  font-size: 1.1rem;
  color: #666;
}

/* Timeline alternative */
.timeline-alt {
  position: relative;
  max-width: 1200px;
  margin: 0 auto;
}

.timeline-alt::after {
  content: '';
  position: absolute;
  width: 2px;
  background-color: var(--secondary-color);
  top: 0;
  bottom: 0;
  left: 50%;
  margin-left: -1px;
}

.timeline-container {
  padding: 10px 40px;
  position: relative;
  background-color: inherit;
  width: 50%;
}

.timeline-container::after {
  content: '';
  position: absolute;
  width: 20px;
  height: 20px;
  right: -10px;
  background-color: #fff;
  border: 4px solid var(--secondary-color);
  top: 15px;
  border-radius: 50%;
  z-index: 1;
}

.left {
  left: 0;
}

.right {
  left: 50%;
}

.left::before {
  content: " ";
  height: 0;
  position: absolute;
  top: 22px;
  width: 0;
  z-index: 1;
  right: 30px;
  border: medium solid #f5f5f5;
  border-width: 10px 0 10px 10px;
  border-color: transparent transparent transparent #f5f5f5;
}

.right::before {
  content: " ";
  height: 0;
  position: absolute;
  top: 22px;
  width: 0;
  z-index: 1;
  left: 30px;
  border: medium solid #f5f5f5;
  border-width: 10px 10px 10px 0;
  border-color: transparent #f5f5f5 transparent transparent;
}

.right::after {
  left: -10px;
}

.timeline-content {
  padding: 20px 30px;
  background-color: #f5f5f5;
  position: relative;
  border-radius: 6px;
}

/* Typing effect */
.typing-effect::after {
  content: '|';
  animation: blink 1s infinite;
}

@keyframes blink {
  0%, 100% { opacity: 1; }
  50% { opacity: 0; }
}

/* Parallax */
.parallax {
  background-attachment: fixed;
  background-position: center;
  background-repeat: no-repeat;
  background-size: cover;
  height: 500px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  text-align: center;
}

.parallax-content {
  background-color: rgba(0, 0, 0, 0.5);
  padding: 2rem;
  border-radius: 8px;
}

/* Utility classes */
.hidden {
  display: none;
}

.visible {
  display: block;
}

.flex {
  display: flex;
}

.flex-center {
  display: flex;
  align-items: center;
  justify-content: center;
}

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

.flex-column {
  display: flex;
  flex-direction: column;
}

.gap-1 {
  gap: 1rem;
}

.gap-2 {
  gap: 2rem;
}

.p-1 {
  padding: 1rem;
}

.p-2 {
  padding: 2rem;
}

.m-1 {
  margin: 1rem;
}

.m-2 {
  margin: 2rem;
}

.rounded {
  border-radius: 8px;
}

.shadow {
  box-shadow: var(--card-shadow);
}

.bg-primary {
  background-color: var(--primary-color);
  color: var(--light-text-color);
}

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

.bg-accent {
  background-color: var(--accent-color);
  color: var(--light-text-color);
}

.bg-light {
  background-color: var(--light-color);
}

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

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

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

.text-light {
  color: var(--light-text-color);
}

.fw-bold {
  font-weight: 700;
}

.fw-medium {
  font-weight: 500;
}

.fs-large {
  font-size: 1.25rem;
}

.fs-xlarge {
  font-size: 1.5rem;
}

.fs-xxlarge {
  font-size: 2rem;
}

.w-100 {
  width: 100%;
}

.h-100 {
  height: 100%;
}

.overflow-hidden {
  overflow: hidden;
}

.position-relative {
  position: relative;
}

.position-absolute {
  position: absolute;
}

.top-0 {
  top: 0;
}

.left-0 {
  left: 0;
}

.right-0 {
  right: 0;
}

.bottom-0 {
  bottom: 0;
}

.z-1 {
  z-index: 1;
}

.z-10 {
  z-index: 10;
}

.z-100 {
  z-index: 100;
}

.z-1000 {
  z-index: 1000;
}