/* CSS Variables */
:root {
    --primary-color: #1a365d;
    --secondary-color: #2c5282;
    --accent-color: #3182ce;
    --text-color: #2d3748;
    --light-text: #718096;
    --background: #ffffff;
    --light-bg: #f7fafc;
    --border-color: #e2e8f0;
    --highlight-color: #ebf8ff;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Open Sans', sans-serif;
    color: var(--text-color);
    line-height: 1.7;
    background: var(--background);
}

.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 20px;
}

a {
    color: var(--accent-color);
    text-decoration: none;
    transition: color 0.3s ease;
}

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

h1, h2, h3 {
    font-family: 'Playfair Display', serif;
    color: var(--primary-color);
    line-height: 1.3;
}

h2 {
    font-size: 1.8rem;
    margin-bottom: 1rem;
    padding-bottom: 0.5rem;
    border-bottom: 2px solid var(--accent-color);
}

h3 {
    font-size: 1.3rem;
    margin: 1.5rem 0 0.75rem;
}

p {
    margin-bottom: 1rem;
}

ul, ol {
    margin-left: 1.5rem;
    margin-bottom: 1rem;
}

li {
    margin-bottom: 0.5rem;
}

/* Navigation */
.navbar {
    background: var(--primary-color);
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

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

.logo {
    font-family: 'Playfair Display', serif;
    font-size: 1.5rem;
    font-weight: 700;
    color: white;
}

.logo:hover {
    color: #ebf8ff;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 2rem;
    margin: 0;
}

.nav-menu li {
    margin: 0;
}

.nav-menu a {
    color: rgba(255,255,255,0.9);
    font-weight: 600;
    padding: 0.5rem 0;
    position: relative;
}

.nav-menu a:hover,
.nav-menu a.active {
    color: white;
}

.nav-menu a.active::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    height: 2px;
    background: white;
}

.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 5px;
}

.nav-toggle span {
    width: 25px;
    height: 3px;
    background: white;
    transition: 0.3s;
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: white;
    padding: 4rem 0;
    text-align: center;
}

.hero h1 {
    font-size: 3rem;
    color: white;
    margin-bottom: 0.5rem;
}

.hero .subtitle {
    font-size: 1.4rem;
    opacity: 0.95;
    margin-bottom: 1.5rem;
}

.event-info {
    background: rgba(255,255,255,0.1);
    display: inline-block;
    padding: 1rem 2rem;
    border-radius: 8px;
    margin-top: 1rem;
}

.event-info p {
    margin: 0.25rem 0;
}

.event-info a {
    color: #90cdf4;
}

.event-info a:hover {
    color: white;
}

/* Page Header */
.page-header {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: white;
    padding: 3rem 0;
    text-align: center;
}

.page-header h1 {
    color: white;
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
}

.page-header .subtitle {
    opacity: 0.9;
    font-size: 1.1rem;
}

/* Content Sections */
main {
    padding: 2rem 0 4rem;
}

.content-section {
    margin-bottom: 3rem;
}

.content-section:last-child {
    margin-bottom: 0;
}

/* Important Dates */
.dates-grid {
    display: grid;
    gap: 0.75rem;
}

.date-item {
    display: flex;
    flex-wrap: wrap;
    gap: 1rem;
    padding: 1rem 1.25rem;
    background: var(--light-bg);
    border-left: 4px solid var(--accent-color);
    border-radius: 0 4px 4px 0;
}

.date-item .date {
    font-weight: 700;
    color: var(--primary-color);
    min-width: 160px;
}

.date-item .event {
    color: var(--text-color);
}

.date-item.highlight {
    background: var(--highlight-color);
    border-left-color: var(--primary-color);
}

.date-item.highlight .date {
    color: var(--primary-color);
}

/* Topics List */
.topics-list {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 0.5rem 2rem;
}

.topics-list li {
    padding-left: 0.5rem;
}

/* Highlights List */
.highlights-list {
    list-style: none;
    margin-left: 0;
}

.highlights-list li {
    padding: 0.75rem 1rem;
    background: var(--light-bg);
    border-radius: 4px;
    margin-bottom: 0.5rem;
}

/* Schedule */
.session-time {
    font-size: 1.1rem;
    color: var(--light-text);
    margin-bottom: 1rem;
}

.schedule-table {
    border: 1px solid var(--border-color);
    border-radius: 8px;
    overflow: hidden;
}

.schedule-item {
    display: flex;
    gap: 1.5rem;
    padding: 1rem 1.25rem;
    border-bottom: 1px solid var(--border-color);
    align-items: flex-start;
}

.schedule-item:last-child {
    border-bottom: none;
}

.schedule-item .time {
    font-weight: 600;
    color: var(--primary-color);
    min-width: 120px;
    font-size: 0.95rem;
}

.schedule-item .event-details {
    flex: 1;
}

.schedule-item .event-title {
    display: block;
    font-weight: 600;
    color: var(--text-color);
    margin-bottom: 0.25rem;
}

.schedule-item .event-desc {
    display: block;
    color: var(--light-text);
    font-size: 0.9rem;
}

.schedule-item .speaker {
    display: block;
    color: var(--accent-color);
    font-size: 0.9rem;
    margin-top: 0.25rem;
}

.schedule-item.keynote {
    background: var(--highlight-color);
}

.schedule-item.panel {
    background: #f0fff4;
}

.lunch-break {
    background: var(--light-bg);
    padding: 1.5rem;
    border-radius: 8px;
    text-align: center;
}

.lunch-break .time {
    display: block;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 0.25rem;
}

.lunch-break .event-title {
    color: var(--light-text);
}

/* Organizers */
.organizers-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin-top: 1.5rem;
}

.organizer-card {
    text-align: center;
    padding: 1.5rem;
    background: var(--light-bg);
    border-radius: 8px;
}

.organizer-photo {
    width: 160px;
    height: 160px;
    border-radius: 50%;
    margin: 0 auto 1rem;
    background: var(--border-color);
    object-fit: cover;
    object-position: center top;
}

.organizer-photo.placeholder {
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, var(--secondary-color), var(--accent-color));
    color: white;
    font-size: 2rem;
}

.organizer-card h3 {
    margin: 0 0 0.25rem;
    font-size: 1.2rem;
}

.organizer-card .affiliation {
    color: var(--light-text);
    font-size: 0.9rem;
    margin-bottom: 0.5rem;
}

.organizer-card .email {
    font-size: 0.85rem;
}

.pc-list {
    column-count: 2;
    column-gap: 2rem;
}

/* TBD Notice */
.tbd-notice {
    background: var(--light-bg);
    border: 2px dashed var(--border-color);
    border-radius: 8px;
    padding: 2rem;
    text-align: center;
}

.tbd-notice h2 {
    border-bottom: none;
    margin-bottom: 1rem;
}

.tbd-notice ul {
    display: inline-block;
    text-align: left;
    margin-top: 1rem;
}

/* Small organizers grid for web chairs */
.organizers-grid.small {
    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
    gap: 1rem;
}

.organizers-grid.small .organizer-card {
    padding: 1rem;
}

.organizers-grid.small .organizer-card h3 {
    font-size: 1rem;
}

/* Footer */
footer {
    background: var(--primary-color);
    color: rgba(255,255,255,0.8);
    padding: 1.5rem 0;
    text-align: center;
}

footer p {
    margin: 0;
    font-size: 0.9rem;
}

/* Mobile Responsive */
@media (max-width: 768px) {
    .nav-toggle {
        display: flex;
    }

    .nav-menu {
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background: var(--primary-color);
        flex-direction: column;
        gap: 0;
        padding: 0;
        max-height: 0;
        overflow: hidden;
        transition: max-height 0.3s ease;
    }

    .nav-menu.active {
        max-height: 300px;
        border-top: 1px solid rgba(255,255,255,0.1);
    }

    .nav-menu li {
        border-bottom: 1px solid rgba(255,255,255,0.1);
    }

    .nav-menu a {
        display: block;
        padding: 1rem 20px;
    }

    .nav-menu a.active::after {
        display: none;
    }

    .nav-toggle.active span:nth-child(1) {
        transform: rotate(45deg) translate(5px, 5px);
    }

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

    .nav-toggle.active span:nth-child(3) {
        transform: rotate(-45deg) translate(7px, -6px);
    }

    .hero h1 {
        font-size: 2rem;
    }

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

    h2 {
        font-size: 1.5rem;
    }

    .date-item {
        flex-direction: column;
        gap: 0.25rem;
    }

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

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

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

    .pc-list {
        column-count: 1;
    }
}