:root {
  --primary: #2c3e50;
  --secondary: #3498db;
  --accent: #e74c3c;
  --light: #f8f9fa;
  --dark: #2c3e50;
  --light-blue: #e1f5fe;
  --purple: #8e44ad;
}

* {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }
        
        body {
            font-family: 'Roboto', sans-serif;
            color: #333;
            line-height: 1.6;
            background-color: #fafafa;
        }
        
        h1, h2, h4 {
            font-family: 'Merriweather', serif;
            color: var(--primary);
            margin-bottom: 1rem;
        }
        
        .container {
            width: 100%;
            max-width: 1200px;
            margin: 0 auto;
            padding: 0 20px;
        }
        
        /* Header Styles */
        header {
            background-color: white;
            box-shadow: 0 2px 10px rgba(0,0,0,0.1);
            position: sticky;
            top: 0;
            z-index: 1000;
        }
        
        .top-bar {
            background-color: var(--primary);
            color: white;
            padding: 8px 0;
            font-size: 0.9rem;
        }
        
        .top-bar-content {
            display: flex;
            justify-content: space-between;
            align-items: center;
        }
        
        .contact-info span {
            margin-right: 15px;
        }
        
        .contact-info i {
            margin-right: 5px;
        }
        
        .main-header {
            padding: 15px 0;
            display: flex;
            justify-content: space-between;
            align-items: center;
        }
        
        .logo-container {
            display: flex;
            align-items: center;
        }
        
        .logo {
            height: 80px;
            margin-right: 15px;
        }
        
        .lab-name h1 {
            font-size: 1.8rem;
            margin-bottom: 5px;
            color: var(--primary);
        }
        
        .lab-name p {
            font-size: 1rem;
            color: #666;
        }
        
        nav ul {
            display: flex;
            list-style: none;
        }
        
        nav ul li {
            margin-left: 20px;
        }
        
        nav ul li a {
            text-decoration: none;
            color: var(--dark);
            font-weight: 500;
            padding: 5px 10px;
            transition: all 0.3s;
            border-bottom: 2px solid transparent;
        }
        
        nav ul li a:hover, 
        nav ul li a.active {
            color: var(--primary);
            border-bottom: 2px solid var(--primary);
        }
        
        .mobile-menu-btn {
            display: none;
            background: none;
            border: none;
            font-size: 1.5rem;
            cursor: pointer;
            color: var(--primary);
        }
        
        /* Hero Section */
        .hero {
            background: linear-gradient(rgba(44, 62, 80, 0.8), rgba(44, 62, 80, 0.8)), url('images/back3.jpg') no-repeat center center/cover;
            color: white;
            padding: 100px 0;
            text-align: center;
        }
        
        .hero-content {
            max-width: 800px;
            margin: 0 auto;
        }
        
        .hero h1 {
            font-size: 2.8rem;
            margin-bottom: 20px;
            color: white;
        }
        
        .hero p {
            font-size: 1.2rem;
            margin-bottom: 30px;
        }
        
        .btn {
            display: inline-block;
            background-color: var(--secondary);
            color: white;
            padding: 12px 30px;
            border-radius: 5px;
            text-decoration: none;
            font-weight: 500;
            transition: all 0.3s;
            border: none;
            cursor: pointer;
        }
        
        .btn:hover {
            background-color: #2980b9;
            transform: translateY(-2px);
            box-shadow: 0 4px 8px rgba(0,0,0,0.1);
        }
        
        /* Section Styles */
        section {
            padding: 80px 0;
        }
        
        .section-header {
            text-align: center;
            margin-bottom: 50px;
            margin-top: 20px;

        }
        
        .section-header h2 {
            font-size: 2.2rem;
            position: relative;
            display: inline-block;
            padding-bottom: 15px;
        }
        
        .section-header h2::after {
            content: '';
            position: absolute;
            bottom: 0;
            left: 50%;
            transform: translateX(-50%);
            width: 80px;
            height: 4px;
            background-color: var(--secondary);
            border-radius: 2px;
        }
        
        /* About Section */
        .about-content {
            display: flex;
            gap: 40px;
            align-items: center;
        }
        
        .about-text {
            flex: 1;
        }
        
        .about-image {
            flex: 1;
            border-radius: 10px;
            overflow: hidden;
            box-shadow: 0 5px 15px rgba(0,0,0,0.1);
        }
        
        .about-image img {
            width: 100%;
            height: auto;
            display: block;
            transition: transform 0.5s;
        }
        
        .about-image img:hover {
            transform: scale(1.05);
        }
        
        .timeline {
            margin-top: 20px;
        }
        
        .timeline-item {
            margin-bottom: 20px;
            padding-left: 20px;
            border-left: 3px solid var(--secondary);
        }
        
        .timeline-item h4 {
            font-size: 1.2rem;
            margin-bottom: 5px;
        }
        
        .timeline-item p {
            color: #666;
        }
        
        /* Research Section */
        .research {
            background-color: var(--light-blue);
        }
        
        .research-content {
            max-width: 900px;
            margin: 0 auto;
        }
        
        .research-content p {
            margin-bottom: 20px;
            font-size: 1.1rem;
        }
        
        .research-focus {
            background-color: white;
            border-radius: 8px;
            padding: 20px;
            margin: 20px 0;
            box-shadow: 0 5px 15px rgba(0,0,0,0.05);
        }
        
        .research-focus h3 {
            color: var(--secondary);
            margin-bottom: 15px;
        }
        
        /* People Section */
        .people-container {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
            gap: 30px;
        }
        
        .people-category {
            margin-bottom: 40px;
        }
        
        .people-category h3 {
            font-size: 1.6rem;
            margin-bottom: 20px;
            padding-bottom: 10px;
            border-bottom: 2px solid var(--secondary);
            display: flex;
            justify-content: space-between;
            align-items: center;
            cursor: pointer;
        }
        
        .people-category h3 .dropdown-icon {
            transition: transform 0.3s;
        }
        
        .people-category.active h3 .dropdown-icon {
            transform: rotate(180deg);
        }
        
        .people-category-content {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
            gap: 20px;
        }
        
        .person-card {
            background-color: white;
            border-radius: 8px;
            overflow: hidden;
            box-shadow: 0 5px 15px rgba(0,0,0,0.05);
            transition: transform 0.3s;
            height: auto;
        }
        
        .person-card:hover {
            transform: translateY(-10px);
            box-shadow: 0 10px 25px rgba(0,0,0,0.1);
        }
        
        .person-img {
            height: 220px;
            overflow: hidden;
            background-color: #f0f0f0;
            display: flex;
            align-items: center;
            justify-content: center;
        }
        .person-img img {
            width: 100%;
            height: 100%;
            object-fit: cover;
            display: block;
        }
        .person-img i {
            font-size: 4rem;
            color: #ccc;
            
        }
        
        .person-info {
            padding: 20px;
        }
        
        .person-info h4 {
            font-size: 1.3rem;
            margin-bottom: 5px;
        }
        
        .person-info .position {
            color: var(--accent);
            font-weight: 500;
            margin-bottom: 10px;
            display: block;
        }
        
        /* News Section */
        .news {
            background-color: var(--light);
        }
        
        .news-item {
            background-color: white;
            border-radius: 8px;
            padding: 20px;
            margin-bottom: 20px;
            box-shadow: 0 5px 15px rgba(0,0,0,0.05);
        }
        
        .news-item h3 {
            color: var(--secondary);
            margin-bottom: 10px;
        }
        
        .news-item .date {
            color: var(--accent);
            font-weight: 500;
            margin-bottom: 10px;
            display: block;
        }
        
        /* Publications */
        .publications {
            background-color: var(--light);
        }
        
        .pub-filter {
            display: flex;
            justify-content: center;
            margin-bottom: 30px;
            flex-wrap: wrap;
            gap: 10px;
        }
        
        .pub-filter button {
            background: none;
            border: 2px solid var(--secondary);
            color: var(--dark);
            padding: 8px 20px;
            border-radius: 30px;
            cursor: pointer;
            transition: all 0.3s;
            font-weight: 500;
        }
        
        .pub-filter button.active, 
        .pub-filter button:hover {
            background-color: var(--secondary);
            color: white;
        }
        
        .pub-list {
            max-height: 600px;
            overflow-y: auto;
            padding: 20px;
            background-color: white;
            border-radius: 8px;
            box-shadow: 0 5px 15px rgba(0,0,0,0.05);
        }
        
        .pub-item {
            padding: 20px 0;
            border-bottom: 1px solid #eee;
        }
        
        .pub-item:last-child {
            border-bottom: none;
        }
        
        .pub-item h3 {
            font-size: 1.2rem;
            margin-bottom: 10px;
            color: var(--primary);
        }
        
        .pub-authors {
            font-style: italic;
            margin-bottom: 8px;
            color: #666;
        }
        
        .pub-journal {
            font-weight: 500;
            color: var(--accent);
            margin-bottom: 8px;
        }
        
        .pub-doi a {
            color: var(--secondary);
            text-decoration: none;
        }
        
        .pub-doi a:hover {
            text-decoration: underline;
        }
         /* Gallery Section */
            .gallery-section {
                background-color: #f5f7fa;
            }

            .gallery-grid {
                display: grid;
                grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
                gap: 1.5rem;
                margin-top: 2rem;
            }

            .gallery-grid img {
                width: 100%;
                height: auto;
                border-radius: 8px;
                object-fit: cover;
                box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
                transition: transform 0.3s ease;
            }

            .gallery-grid img:hover {
                transform: scale(2);
            }
            .hidden {
                display: none;
            }


        
        /* Contact Section */
        .contact {
            background-color: var(--light);
        }
        
        .contact-container {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
            gap: 40px;
        }
        
        .contact-info {
            background-color: white;
            padding: 30px;
            border-radius: 8px;
            box-shadow: 0 5px 15px rgba(0,0,0,0.05);
        }
        
        .contact-info h3 {
            margin-bottom: 20px;
            padding-bottom: 10px;
            border-bottom: 2px solid var(--secondary);
        }
        
        .contact-detail {
            display: flex;
            margin-bottom: 20px;
        }
        
        .contact-icon {
            width: 50px;
            height: 50px;
            background-color: var(--light-blue);
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            margin-right: 15px;
            flex-shrink: 0;
        }
        
        .contact-icon i {
            color: var(--primary);
            font-size: 1.2rem;
        }
        
        .contact-text h4 {
            margin-bottom: 5px;
            font-size: 1.1rem;
        }
        
        .map-container {
            height: 400px;
            border-radius: 8px;
            overflow: hidden;
            box-shadow: 0 5px 15px rgba(0,0,0,0.1);
        }
        
        .map-container iframe {
            width: 100%;
            height: 100%;
            border: none;
        }
        
        /* Footer */
        footer {
            background-color: var(--primary);
            color: white;
            padding: 40px 0 20px;
        }
        
        .footer-content {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
            gap: 30px;
            margin-bottom: 30px;
        }
        
        .footer-logo {
            margin-bottom: 20px;
        }
        
        .footer-logo img {
            height: 80px;
        }
        
        .footer-about p {
            margin-bottom: 20px;
        }
        
        .social-links {
            display: flex;
            gap: 15px;
        }
        
        .social-links 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: white;
            text-decoration: none;
            transition: all 0.3s;
        }
        
        .social-links a:hover {
            background-color: var(--secondary);
            transform: translateY(-5px);
        }
        
        .footer-links h3, .footer-contact h3 {
            margin-bottom: 20px;
            font-size: 1.3rem;
        }
        
        .footer-links ul {
            list-style: none;
        }
        
        .footer-links li {
            margin-bottom: 10px;
        }
        
        .footer-links a {
            color: rgba(255,255,255,0.8);
            text-decoration: none;
            transition: all 0.3s;
        }
        
        .footer-links a:hover {
            color: white;
            padding-left: 5px;
        }
        
        .footer-contact p {
            margin-bottom: 10px;
            display: flex;
            align-items: flex-start;
        }
        
        .footer-contact i {
            margin-right: 10px;
            margin-top: 5px;
        }
        
        .copyright {
            text-align: center;
            padding-top: 20px;
            border-top: 1px solid rgba(255,255,255,0.1);
            font-size: 0.9rem;
            color: rgba(255,255,255,0.7);
        }
        
        /* Responsive Design */
        @media (max-width: 992px) {
            .about-content {
                flex-direction: column;
            }
            
            .hero h1 {
                font-size: 2.2rem;
            }
        }
        
        @media (max-width: 768px) {
            .mobile-menu-btn {
                display: block;
            }
            
            nav ul {
                display: none;
                position: absolute;
                top: 100%;
                left: 0;
                width: 100%;
                background-color: white;
                flex-direction: column;
                box-shadow: 0 5px 10px rgba(0,0,0,0.1);
                padding: 20px 0;
            }
            
            nav ul.show {
                display: flex;
            }
            
            nav ul li {
                margin: 10px 0;
                text-align: center;
            }
            
            .hero {
                padding: 60px 0;
            }
            
            .hero h1 {
                font-size: 1.8rem;
            }
            
            section {
                padding: 60px 0;
            }
            
            .section-header h2 {
                font-size: 1.8rem;
            }
        }
        
        @media (max-width: 576px) {
            .top-bar-content {
                flex-direction: column;
                gap: 5px;
            }
            
            .hero h1 {
                font-size: 1.6rem;
            }
            
            .btn {
                padding: 10px 20px;
            }
        }

/* Design and Developed by Suman Kumar Chakraborty */