:root {
    --primary: #0a2342;
    --secondary: #0b8a9d;
    --accent: #f68e1f;
    --light: #f5f5f5;
    --dark: #191919;
    --transition: all 0.3s ease;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

body {
    background-color: var(--light);
    color: var(--dark);
    line-height: 1.6;
    overflow-x: hidden;
    position: relative;
}

.bg-grid {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-image: 
        linear-gradient(to right, rgba(10, 35, 66, 0.05) 1px, transparent 1px),
        linear-gradient(to bottom, rgba(10, 35, 66, 0.05) 1px, transparent 1px);
    background-size: 20px 20px;
    z-index: -1;
}

body.dark-mode .bg-grid {
    background-image: 
        linear-gradient(to right, rgba(255, 255, 255, 0.05) 1px, transparent 1px),
        linear-gradient(to bottom, rgba(255, 255, 255, 0.05) 1px, transparent 1px);
}

.particle {
    position: absolute;
    border-radius: 50%;
    background: var(--secondary);
    opacity: 0.2;
    pointer-events: none;
}

header {
    padding: 1.5rem 0;
    position: fixed;
    width: 100%;
    z-index: 100;
    transition: var(--transition);
    background-color: rgb(245, 245, 245);
    backdrop-filter: blur(5px);
    border-bottom: 1px solid var(--secondary);
}

header.scrolled {
    box-shadow: 0 5px 20px rgba(0, 0, 0, 0.1);
    padding: 1rem 0;
}

.container {
    width: 85%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

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

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary);
    text-decoration: none;
    display: flex;
    align-items: center;
}

.logo span {
    color: var(--secondary);
    margin-right: 5px;
}

.nav-links {
    display: flex;
    list-style: none;
}

.nav-links li {
    margin-left: 2rem;
}

.nav-links a {
    text-decoration: none;
    color: var(--dark);
    font-weight: 500;
    position: relative;
    transition: var(--transition);
    font-size: 1.3rem;
}

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

.nav-links a::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 0;
    height: 2px;
    background-color: var(--secondary);
    transition: var(--transition);
}

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

.mode-toggle {
    background: none;
    border: none;
    cursor: pointer;
    font-size: 1.2rem;
    color: var(--dark);
    transition: var(--transition);
}

.mode-toggle:hover {
    color: var(--secondary);
    transform: rotate(30deg);
}

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

.section {
    padding: 100px 0;
    position: relative;
}

#about {
    padding-top: 150px;
    min-height: 100vh;
    display: flex;
    align-items: center;
}

.section-title {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    color: var(--primary);
    text-align: center;
    position: relative;
}

.section-title::after {
    content: '';
    position: absolute;
    bottom: -10px;
    left: 50%;
    transform: translateX(-50%);
    width: 50px;
    height: 3px;
    background-color: var(--secondary);
}

.section-subtitle {
    text-align: center;
    margin-bottom: 3rem;
    color: var(--secondary);
    font-weight: 500;
}

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

.about-image {
    width: 300px;
    height: 300px;
    border-radius: 20px;
    overflow: hidden;
    margin-right: 40px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
    position: relative;
}

.about-image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: var(--transition);
}

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

.about-text {
    flex: 1;
    min-width: 300px;
    z-index: 2;
}

.about-text h1 {
    font-size: 3rem;
    margin-bottom: 0.5rem;
    color: var(--primary);
}

.about-text h3 {
    font-size: 1.5rem;
    margin-bottom: 1.5rem;
    color: var(--secondary);
    font-weight: 500;
}

.about-text p {
    margin-bottom: 1.5rem;
}

.hero-buttons {
    margin-top: 2rem;
}

.btn {
    display: inline-block;
    padding: 0.8rem 1.8rem;
    border-radius: 30px;
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
    margin-right: 1rem;
    border: 2px solid transparent;
}

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

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

.btn-secondary {
    background-color: transparent;
    border-color: var(--primary);
    color: var(--primary);
}

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

.hero-visual {
    position: absolute;
    right: 10%;
    top: 30%;
    transform: translateY(-50%);
    width: 45%;
    height: 70%;
    overflow: hidden;
    border-radius: 10px;
    box-shadow: 0 0px 0px rgba(0, 0, 0, 0.1);
    opacity: 1;
    animation: fadeIn 0.8s ease forwards 1.2s;
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 0;
}

.data-visualization {
    position: relative;
    width: 100%;
    height: 100%;
}

.timeline {
  position: relative;
  margin-top: 3rem;
  padding-left: 50px;
}

.timeline-item {
  position: relative;
  margin-bottom: 30px;
}

.timeline-icon {
  position: absolute;
  left: 0;
  top: 40%;
  width: 30px;
  height: 30px;
  background-color: var(--secondary);
  color: white;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1rem;
  z-index: 2;
}

.timeline-content {
  background: #fff;
  padding: 20px 25px;
  border-radius: 10px;
  margin-left: 50px;
  box-shadow: 0 10px 25px rgba(0,0,0,0.05);
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}

body.dark-mode .timeline-content {
  background-color: #222;
}
  
  .timeline-item:hover .timeline-content {
    transform: translateY(-5px);
    box-shadow: 0 20px 30px rgba(0,0,0,0.1);
  }
  
  .timeline-date {
    display: block;
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--secondary);
    margin-bottom: 10px;
  }
  

  
  /* expandable coursework */
  .expandable .expand-btn {
    margin-top: 15px;
    background: none;
    border: none;
    color: var(--secondary);
    font-weight: 600;
    cursor: pointer;
    font-size: 0.95rem;
    display: flex;
    align-items: center;
    
  }
  
  .expandable .expand-btn i {
    margin-left: 5px;
    transition: transform 0.3s ease;
  }
  
  .coursework-list {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s ease;
    padding-left: 1rem;
    list-style: disc inside;
  }
  
  .expanded .coursework-list {
    max-height: 500px;
  }
  
  .expanded .expand-btn i {
    transform: rotate(180deg);
    transition: transform 0.3s ease;
  }



  /* expandable experience detials */
  .expandable .expand-btn-exp {
    margin-top: 15px;
    background: none;
    border: none;
    color: var(--secondary);
    font-weight: 600;
    cursor: pointer;
    font-size: 0.95rem;
    display: flex;
    align-items: center;
  }
  
  .expandable .expand-btn-exp i {
    margin-left: 5px;
    transition: transform 0.3s ease;
  }

  .details-list{
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s ease;
    padding-left: 1rem;
    list-style: disc inside;
  }
  
  .expanded .details-list {
    max-height: 500px;
}
  
  .expanded .expand-btn-exp i {
    transform: rotate(180deg);
    transition: transform 0.3s ease;
  }


  .expand-btn i,
  .expand-btn-exp i {
      transition: transform 0.3s ease;
  }



.skills-container {
    margin-top: 50px;
}

.skills-categories {
    display: flex;
    justify-content: center;
    margin-bottom: 2rem;
    flex-wrap: wrap;
}

.skill-category {
    background: none;
    border: none;
    padding: 0.5rem 1.5rem;
    border-radius: 20px;
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    margin: 5px;
    color: var(--dark);
}

.skill-category.active {
    background-color: var(--secondary);
    color: var(--light);
}

.skills-grid {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 20px;
}

.skill-item {
    background-color: rgba(255, 255, 255, 0.9);
    border-radius: 10px;
    padding: 1.2rem;
    text-align: center;
    transition: var(--transition);
    width: 120px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.05);
    position: relative;
    overflow: visible;
}

.skill-item:hover {
    transform: translateY(-10px);
    box-shadow: 0 15px 30px rgba(0, 0, 0, 0.1);
}

.skill-item::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 4px;
    background-color: var(--secondary);
    transform: scaleX(0);
    transform-origin: left;
    transition: var(--transition);
}

.skill-item:hover::before {
    transform: scaleX(1);
}


.skill-item[data-tooltip] {
    position: relative;
}

.skill-item[data-tooltip]::after {
    content: attr(data-tooltip);
    position: absolute;
    bottom: calc(100% + 10px);
    left: 50%;
    transform: translateX(-50%);
    background: var(--secondary); 
    color: var(--light);          
    padding: 10px 14px;          
    border-radius: 10px;
    font-size: 1.15rem;        
    font-weight: 500;
    white-space: nowrap;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.3s ease, transform 0.3s ease;
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.2);
    z-index: 999;
}

.skill-item[data-tooltip]:hover::after {
    opacity: 1;
    transform: translateX(-50%) translateY(-5px);
}



.skill-icon {
    font-size: 2rem;
    margin-bottom: 0.8rem;
    color: var(--secondary);
}

.skill-name {
    font-weight: 600;
}


.projects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 30px;
    margin-top: 50px;
}

.project-card {
    background-color: white;
    border-radius: 15px;
    overflow: hidden;
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.05);
    transition: var(--transition);
    position: relative;
    height: 350px;
}

.project-card:hover {
    transform: translateY(-10px);
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.1);
}


.project-card:hover{
    transform: scale(1.05);
}

.project-content {
    padding: 20px;
}

.project-title {
    font-size: 1.2rem;
    font-weight: 600;
    margin-bottom: 10px;
    color: var(--primary);
}

.project-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 15px;
}

.project-tag {
    background-color: rgba(11, 138, 157, 0.1);
    color: var(--secondary);
    padding: 4px 10px;
    border-radius: 20px;
    font-size: 0.8rem;
}

.project-description {
    font-size: 0.9rem;
    margin-bottom: 20px;
    display: -webkit-box;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.project-links {
    display: flex;
    gap: 15px;
}

.project-link {
    color: var(--dark);
    text-decoration: none;
    font-size: 0.9rem;
    font-weight: 500;
    transition: var(--transition);
    display: flex;
    align-items: center;
}

.project-link i {
    margin-right: 5px;
}

.project-link:hover {
    color: var(--secondary);
}


.publications-container {
    margin-top: 50px;
}

.publication-card {
    background-color: white;
    border-radius: 15px;
    padding: 25px;
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.05);
    transition: var(--transition);
    margin-bottom: 30px;
    cursor: pointer;
    position: relative;
    overflow: hidden;
}

.publication-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 15px 30px rgba(0, 0, 0, 0.1);
}

.publication-card::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    height: 100%;
    width: 5px;
    background-color: var(--secondary);
    transform: scaleY(0);
    transform-origin: bottom;
    transition: var(--transition);
}

.publication-card:hover::before {
    transform: scaleY(1);
}

.publication-title {
    font-size: 1.3rem;
    font-weight: 600;
    margin-bottom: 10px;
    color: var(--primary);
}

.publication-journal {
    font-style: italic;
    color: var(--secondary);
    margin-bottom: 15px;
}

.publication-abstract {
    max-height: 0;
    overflow: hidden;
    transition: var(--transition);
    margin-bottom: 0;
}

.publication-card.expanded .publication-abstract {
    max-height: 300px;
    margin-bottom: 15px;
}

.publication-toggle {
    font-size: 0.9rem;
    color: var(--secondary);
    background: none;
    border: none;
    cursor: pointer;
    display: flex;
    align-items: center;
}

.publication-toggle i {
    margin-left: 5px;
    transition: var(--transition);
}

.publication-actions {
    display: flex;
    gap: 15px;
    margin-top: 15px;
    align-items: center;
}

.btn-view-paper {
    background-color: var(--secondary);
    color: var(--light);
    padding: 0.5rem 1rem;
    border: none;
    border-radius: 20px;
    text-decoration: none;
    font-size: 0.9rem;
    font-weight: 500;
    transition: var(--transition);
    display: inline-flex;
    align-items: center;
}

.btn-view-paper i {
    margin-left: 6px;
}

.btn-view-paper:hover {
    background-color: var(--primary);
    color: var(--light);
}

.publication-card.expanded .publication-toggle i {
    transform: rotate(180deg);
}

.contact-container {
    display: flex;
    margin-top: 50px;
    gap: 50px;
    flex-wrap: wrap;
}

.contact-info {
    flex: 1;
    min-width: 300px;
}

.contact-info h3 {
    font-size: 1.8rem;
    margin-bottom: 1.5rem;
    color: var(--primary);
}

.contact-info h3 {
    font-size: 1.8rem;
    margin-bottom: 1.5rem;
    color: var(--primary);
}

.contact-info p {
    margin-bottom: 2rem;
}

.contact-methods {
    list-style: none;
}

.contact-method {
    display: flex;
    align-items: center;
    margin-bottom: 1.5rem;
}

.contact-method i {
    width: 40px;
    height: 40px;
    background-color: rgba(11, 138, 157, 0.1);
    color: var(--secondary);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-right: 15px;
    transition: var(--transition);
}

.contact-method:hover i {
    background-color: var(--secondary);
    color: var(--light);
}

.contact-method a {
    text-decoration: none;
    color: var(--dark);
    transition: var(--transition);
}

.contact-method:hover a {
    color: var(--secondary);
}

.social-links {
    display: flex;
    gap: 15px;
    margin-top: 2rem;
}

.social-link {
    width: 40px;
    height: 40px;
    background-color: var(--light);
    color: var(--dark);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    text-decoration: none;
    transition: var(--transition);
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
}

.social-link:hover {
    background-color: var(--secondary);
    color: var(--light);
    transform: translateY(-5px);
}

.contact-form {
    flex: 1;
    min-width: 300px;
}

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

.form-control {
    width: 100%;
    padding: 0.8rem 1rem;
    border: 1px solid #e0e0e0;
    border-radius: 5px;
    font-size: 1rem;
    transition: var(--transition);
}

.form-control:focus {
    outline: none;
    border-color: var(--secondary);
    box-shadow: 0 0 0 3px rgba(11, 138, 157, 0.1);
}

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

.btn-submit {
    background-color: var(--secondary);
    color: var(--light);
    border: none;
    padding: 0.8rem 1.8rem;
    border-radius: 30px;
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    display: inline-flex;
    align-items: center;
}

.btn-submit i {
    margin-left: 8px;
}

.btn-submit:hover {
    background-color: var(--primary);
    transform: translateY(-3px);
}

footer {
    background-color: var(--primary);
    color: var(--light);
    padding: 3rem 0;
}

.footer-content {
    display: flex;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 30px;
}

.footer-logo {
    flex: 1;
    min-width: 250px;
}

.footer-logo h3 {
    font-size: 1.5rem;
    margin-bottom: 1rem;
}

.footer-logo p {
    margin-bottom: 1.5rem;
    opacity: 0.8;
}

.footer-links {
    flex: 1;
    min-width: 250px;
}

.footer-links h4 {
    font-size: 1.2rem;
    margin-bottom: 1.5rem;
}

.footer-nav {
    list-style: none;
}

.footer-nav li {
    margin-bottom: 0.8rem;
}

.footer-nav a {
    text-decoration: none;
    color: var(--light);
    opacity: 0.8;
    transition: var(--transition);
}

.footer-nav a:hover {
    opacity: 1;
    color: var(--secondary);
}

.footer-contact {
    flex: 1;
    min-width: 250px;
}

.footer-contact h4 {
    font-size: 1.2rem;
    margin-bottom: 1.5rem;
}

.footer-contact p {
    margin-bottom: 0.8rem;
    opacity: 0.8;
    display: flex;
    align-items: center;
}

.footer-contact p i {
    margin-right: 10px;
    color: var(--secondary);
}

.copyright {
    text-align: center;
    padding-top: 2rem;
    margin-top: 2rem;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    font-size: 0.9rem;
    opacity: 0.8;
}


@keyframes fadeUp {
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes fadeIn {
    to {
        opacity: 1;
    }
}


body.dark-mode {
    background-color: var(--dark);
    color: var(--light);
}

body.dark-mode header {
    background-color: rgb(25, 25, 25);
}

body.dark-mode .logo {
    color: var(--light);
}

body.dark-mode .nav-links a {
    color: var(--light);
}

body.dark-mode .mode-toggle {
    color: var(--light);
}

body.dark-mode .section-title {
    color: var(--light);
}

body.dark-mode .about-text h1 {
    color: var(--light);
}

body.dark-mode .skill-item {
    background-color: rgba(40, 40, 40, 0.9);
}

body.dark-mode .project-card {
    background-color: #222;
}

body.dark-mode .project-title {
    color: var(--light);
}

body.dark-mode .project-link {
    color: var(--light);
}

body.dark-mode .project-link:hover {
    color: var(--secondary);
}

body.dark-mode .publication-card {
    background-color: #222;
}

body.dark-mode .publication-title {
    color: var(--light);
}

body.dark-mode .form-control {
    background-color: #333;
    border-color: #444;
    color: var(--light);
}

body.dark-mode .skill-category {
    color: var(--light);
}

body.dark-mode .skill-category.active {
    background-color: var(--secondary);
    color: var(--light);
}


@media (max-width: 992px) {
    .about-text h1 {
        font-size: 2.8rem;
    }

    .hero-visual {
        width: 40%;
    }
}

@media (max-width: 768px) {
    .hero-visual {
        display: none;
    }

    .hamburger {
        display: block;
    }

    .nav-links {
        position: fixed;
        top: 0;
        right: -300px;
        width: 300px;
        height: 100vh;
        background-color: var(--light);
        flex-direction: column;
        justify-content: flex-start;
        padding-top: 80px;
        transition: var(--transition);
        box-shadow: -5px 0 30px rgba(0, 0, 0, 0.1);
        z-index: 99;
    }

    body.dark-mode .nav-links {
        background-color: var(--dark);
    }

    .nav-links.active {
        right: 0;
    }

    .nav-links li {
        margin: 0;
        width: 100%;
        text-align: center;
    }

    .nav-links a {
        display: block;
        padding: 1rem 0;
    }

    .nav-links a::after {
        display: none;
    }

}

@media (max-width: 576px) {
    .about-text h1 {
        font-size: 2.2rem;
    }

    .about-text h3 {
        font-size: 1.2rem;
    }

    .hero-buttons {
        display: flex;
        flex-direction: column;
        gap: 10px;
    }

    .btn {
        margin-right: 0;
        text-align: center;
    }

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