/* Root Variables */
:root {
    --primary-blue: #1d5075;
    --dark-blue: #163d58;
    --light-blue: #2a6892;
    --gray-50: #f9fafb;
    --gray-100: #f3f4f6;
    --gray-200: #e5e7eb;
    --gray-300: #d1d5db;
    --gray-400: #9ca3af;
    --gray-500: #6b7280;
    --gray-600: #4b5563;
    --gray-700: #374151;
    --gray-800: #1f2937;
    --gray-900: #111827;
    --white: #ffffff;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow: 0 1px 3px 0 rgb(0 0 0 / 0.1), 0 1px 2px -1px rgb(0 0 0 / 0.1);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);
}

/* Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    font-size: 16px;
    line-height: 1.6;
    color: var(--gray-800);
    background-color: var(--white);
}

/* Navigation */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background-color: var(--white);
    box-shadow: var(--shadow-md);
    z-index: 1000;
    transition: all 0.3s ease;
}

.navbar.scrolled {
    box-shadow: var(--shadow-lg);
}

.navbar .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    max-width: 1200px;
    margin: 0 auto;
    padding: 1rem 2rem;
}

.nav-brand {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--primary-blue);
    text-decoration: none;
}

.nav-toggle {
    display: none;
    flex-direction: column;
    background: none;
    border: none;
    cursor: pointer;
    padding: 0.5rem;
    gap: 0;
}

.nav-toggle span {
    width: 25px;
    height: 3px;
    background-color: var(--gray-700);
    margin: 3px 0;
    transition: all 0.3s ease;
    border-radius: 2px;
}

.nav-toggle.active span:nth-child(1) {
    transform: rotate(45deg) translate(7px, 7px);
}

.nav-toggle.active span:nth-child(2) {
    opacity: 0;
}

.nav-toggle.active span:nth-child(3) {
    transform: rotate(-45deg) translate(7px, -7px);
}

.nav-links {
    display: flex;
    list-style: none;
    gap: 2rem;
}

.nav-links a {
    color: var(--gray-700);
    text-decoration: none;
    font-weight: 500;
    font-size: 0.95rem;
    transition: color 0.3s ease;
    position: relative;
}

.nav-links a::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 0;
    height: 2px;
    background-color: var(--primary-blue);
    transition: width 0.3s ease;
}

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

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

/* Hero Section */
.hero {
    position: relative;
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background-image: url('images/background.png');
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
    overflow: hidden;
    margin-top: 60px;
}

.hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.3);
    pointer-events: none;
}

.hero-overlay {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: transparent;
}

.hero-content {
    position: relative;
    z-index: 1;
    text-align: center;
    color: var(--white);
    padding: 2rem;
    max-width: 900px;
}

.hero-title {
    font-size: 4rem;
    font-weight: 700;
    margin-bottom: 1rem;
    text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.2);
}

.hero-subtitle {
    font-size: 1.5rem;
    font-weight: 400;
    margin-bottom: 1rem;
    text-shadow: 1px 1px 2px rgba(0, 0, 0, 0.2);
}

.hero-meta {
    font-size: 1.1rem;
    font-weight: 500;
    margin-bottom: 0.5rem;
    opacity: 0.95;
}

.hero-location {
    font-size: 1.3rem;
    font-weight: 600;
    margin-bottom: 2rem;
}

.hero-buttons {
    display: flex;
    gap: 1rem;
    justify-content: center;
    flex-wrap: wrap;
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 0.875rem 2rem;
    font-size: 1rem;
    font-weight: 600;
    text-decoration: none;
    border-radius: 0.5rem;
    transition: all 0.3s ease;
    cursor: pointer;
    border: none;
}

.btn-primary {
    background-color: var(--white);
    color: var(--primary-blue);
}

.btn-primary:hover {
    background-color: var(--gray-100);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

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

.btn-secondary:hover {
    background-color: var(--white);
    color: var(--primary-blue);
    transform: translateY(-2px);
}

/* Sections */
.section {
    padding: 5rem 2rem;
}

.section-white {
    background-color: var(--white);
}

.section-gray {
    background-color: var(--gray-50);
}

.container {
    max-width: 1200px;
    margin: 0 auto;
}

.section-title {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--gray-900);
    text-align: center;
    margin-bottom: 1rem;
}

.section-divider {
    width: 80px;
    height: 4px;
    background: linear-gradient(to right, var(--primary-blue), var(--light-blue));
    margin: 0 auto 3rem;
    border-radius: 2px;
}

/* Scope Section */
.scope-content {
    max-width: 900px;
    margin: 0 auto;
}

.lead {
    font-size: 1.25rem;
    font-weight: 500;
    color: var(--gray-700);
    margin-bottom: 1.5rem;
    line-height: 1.8;
}

.scope-content p {
    margin-bottom: 1.5rem;
    color: var(--gray-700);
}

.scope-list {
    list-style: none;
    margin: 2rem 0;
}

.scope-list li {
    padding: 1rem;
    margin-bottom: 1rem;
    background-color: var(--gray-50);
    border-left: 4px solid var(--primary-blue);
    border-radius: 0.5rem;
    transition: all 0.3s ease;
}

.scope-list li:hover {
    background-color: var(--white);
    box-shadow: var(--shadow-md);
    transform: translateX(4px);
}

.scope-list strong {
    color: var(--primary-blue);
}

/* CFP Section */
.cfp-intro {
    text-align: center;
    font-size: 1.1rem;
    color: var(--gray-700);
    margin-bottom: 3rem;
    max-width: 800px;
    margin-left: auto;
    margin-right: auto;
}

.topics-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 1.5rem;
    margin-bottom: 3rem;
}

.topic-card {
    background-color: var(--white);
    border-radius: 0.75rem;
    box-shadow: var(--shadow);
    padding: 1.5rem;
    transition: all 0.3s ease;
}

.topic-card:hover {
    box-shadow: var(--shadow-lg);
    transform: translateY(-4px);
}

.topic-card h3 {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--primary-blue);
    margin: 0 0 0.75rem 0;
}

.topic-card p {
    margin: 0;
    color: var(--gray-700);
    line-height: 1.7;
}

.submission-info {
    text-align: center;
    margin-top: 4rem;
    padding: 2rem;
    background-color: var(--white);
    border-radius: 0.75rem;
    box-shadow: var(--shadow-md);
}

.submission-info h3 {
    font-size: 1.5rem;
    color: var(--gray-900);
    margin-bottom: 1rem;
}

.submission-info p {
    color: var(--gray-700);
    margin-bottom: 1.5rem;
    max-width: 700px;
    margin-left: auto;
    margin-right: auto;
}

/* Dates Section */
.dates-timeline {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin-bottom: 2rem;
}

.date-card {
    background-color: var(--white);
    padding: 2rem;
    border-radius: 0.75rem;
    box-shadow: var(--shadow-md);
    text-align: center;
    transition: all 0.3s ease;
}

.date-card:hover {
    box-shadow: var(--shadow-xl);
    transform: translateY(-4px);
}

.date-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.date-content h3 {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--gray-800);
    margin-bottom: 0.5rem;
}

.date-value {
    font-size: 1.3rem;
    font-weight: 700;
    color: var(--primary-blue);
}

.dates-note {
    text-align: center;
    color: var(--gray-600);
    font-style: italic;
    margin-top: 2rem;
}

/* Organizers Section */
.organizers-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 3rem;
    justify-items: center;
}

.organizer-card {
    background-color: var(--white);
    padding: 2rem;
    border-radius: 0.75rem;
    box-shadow: var(--shadow-md);
    text-align: center;
    transition: all 0.3s ease;
    max-width: 320px;
    width: 100%;
}

.organizer-card:hover {
    box-shadow: var(--shadow-xl);
    transform: translateY(-4px);
}

.organizer-photo {
    width: 200px;
    height: 200px;
    margin: 0 auto 1.5rem;
    border-radius: 50%;
    overflow: hidden;
    border: 4px solid var(--primary-blue);
}

.organizer-photo img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.organizer-card h3 {
    font-size: 1.3rem;
    font-weight: 600;
    color: var(--gray-900);
    margin-bottom: 0.5rem;
}

.organizer-title {
    font-size: 1rem;
    color: var(--gray-600);
    margin-bottom: 0.25rem;
}

.organizer-affiliation {
    font-size: 1rem;
    font-weight: 600;
    color: var(--primary-blue);
    margin-bottom: 1rem;
}

.organizer-links {
    display: flex;
    gap: 1rem;
    justify-content: center;
}

.organizer-link {
    color: var(--gray-600);
    text-decoration: none;
    font-size: 0.9rem;
    transition: color 0.3s ease;
}

.organizer-link:hover {
    color: var(--primary-blue);
}

/* TPC Section */
.tpc-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 1.5rem;
    margin-top: 2rem;
}

.tpc-member {
    background-color: var(--gray-50);
    padding: 1.5rem;
    border-radius: 0.5rem;
    transition: all 0.3s ease;
    border-left: 3px solid var(--primary-blue);
}

.tpc-member:hover {
    background-color: var(--white);
    box-shadow: var(--shadow-md);
    transform: translateY(-2px);
}

.tpc-member h3 {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--gray-900);
    margin-bottom: 0.5rem;
}

.tpc-member p {
    font-size: 0.95rem;
    color: var(--gray-600);
    margin: 0;
    line-height: 1.5;
}

/* Schedule Section */
.schedule-note {
    text-align: center;
    color: var(--gray-600);
    font-style: italic;
    margin-bottom: 3rem;
}

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

.schedule-item {
    display: flex;
    gap: 2rem;
    margin-bottom: 2rem;
    padding: 1.5rem;
    background-color: var(--white);
    border-radius: 0.75rem;
    box-shadow: var(--shadow);
    transition: all 0.3s ease;
}

.schedule-item:hover {
    box-shadow: var(--shadow-lg);
    transform: translateX(4px);
}

.schedule-time {
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--primary-blue);
    min-width: 100px;
}

.schedule-details h3 {
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--gray-900);
    margin-bottom: 0.5rem;
}

.schedule-details p {
    color: var(--gray-600);
    margin: 0;
}

/* Venue Section */
.venue-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 3rem;
    align-items: center;
}

.venue-info h3 {
    font-size: 2rem;
    font-weight: 700;
    color: var(--gray-900);
    margin-bottom: 1rem;
}

.venue-location {
    font-size: 1.3rem;
    font-weight: 600;
    color: var(--primary-blue);
    margin-bottom: 1.5rem;
}

.venue-description {
    color: var(--gray-700);
    line-height: 1.8;
    margin-bottom: 2rem;
}

.venue-image {
    border-radius: 0.75rem;
    overflow: hidden;
    box-shadow: var(--shadow-xl);
}

.venue-image img {
    width: 100%;
    height: auto;
    display: block;
}

/* Contact Section */
.contact-content {
    text-align: center;
    max-width: 600px;
    margin: 0 auto;
}

.contact-content p {
    color: var(--gray-700);
    margin-bottom: 1.5rem;
}

.contact-email {
    display: inline-block;
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--primary-blue);
    text-decoration: none;
    margin-bottom: 2rem;
    transition: all 0.3s ease;
}

.contact-email:hover {
    color: var(--dark-blue);
    transform: scale(1.05);
}

.social-links {
    display: flex;
    gap: 1.5rem;
    justify-content: center;
}

.social-link {
    color: var(--gray-600);
    text-decoration: none;
    font-weight: 500;
    padding: 0.5rem 1rem;
    border-radius: 0.5rem;
    transition: all 0.3s ease;
}

.social-link:hover {
    color: var(--primary-blue);
    background-color: var(--gray-100);
}

/* Footer */
.footer {
    background-color: var(--gray-900);
    color: var(--gray-300);
    padding: 3rem 2rem 1.5rem;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin-bottom: 2rem;
}

.footer-section h4 {
    color: var(--white);
    font-size: 1.2rem;
    margin-bottom: 1rem;
}

.footer-section p {
    color: var(--gray-400);
    line-height: 1.6;
}

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

.footer-links li {
    margin-bottom: 0.5rem;
}

.footer-links a,
.footer-section a {
    color: var(--gray-400);
    text-decoration: none;
    transition: color 0.3s ease;
}

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

.footer-bottom {
    border-top: 1px solid var(--gray-700);
    padding-top: 1.5rem;
    text-align: center;
    color: var(--gray-500);
}

.footer-bottom p {
    margin: 0.25rem 0;
}

.footer-bottom a {
    color: var(--gray-400);
    text-decoration: none;
}

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

/* Responsive Design */
@media (max-width: 768px) {
    .navbar .container {
        padding: 1rem 1.5rem;
    }

    .nav-brand {
        font-size: 1.1rem;
    }

    .nav-toggle {
        display: flex;
        z-index: 1001;
    }

    .nav-links {
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background-color: var(--white);
        flex-direction: column;
        padding: 0;
        box-shadow: var(--shadow-lg);
        gap: 0;
        max-height: 0;
        overflow: hidden;
        transition: max-height 0.3s ease-in-out;
        opacity: 0;
        visibility: hidden;
    }

    .nav-links.active {
        max-height: 500px;
        padding: 1rem 2rem;
        opacity: 1;
        visibility: visible;
    }

    .nav-links li {
        margin: 0.5rem 0;
    }

    .nav-links a {
        display: block;
        padding: 0.75rem 0;
        font-size: 1rem;
    }

    .hero {
        margin-top: 70px;
    }

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

    .hero-subtitle {
        font-size: 1.2rem;
    }

    .hero-location {
        font-size: 1.1rem;
    }

    .section {
        padding: 3rem 1.5rem;
    }

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

    .topics-grid {
        grid-template-columns: 1fr;
    }

    .dates-timeline {
        grid-template-columns: 1fr;
    }

    .organizers-grid {
        grid-template-columns: 1fr;
    }

    .tpc-grid {
        grid-template-columns: 1fr;
    }

    .schedule-item {
        flex-direction: column;
        gap: 0.5rem;
    }

    .schedule-time {
        min-width: auto;
    }

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

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

@media (max-width: 480px) {
    .hero-title {
        font-size: 2rem;
    }

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

    .hero-buttons {
        flex-direction: column;
    }

    .btn {
        width: 100%;
    }
}