:root {
    --primary-color: #2c3e50;
    --secondary-color: #3498db;
    --accent-color: #e74c3c;
    --light-bg: #f8f9fa;
    --dark-text: #333;
    --light-text: #fff;
    --font-main: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

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

body {
    font-family: var(--font-main);
    line-height: 1.6;
    color: var(--dark-text);
    background-color: #fff;
}

/* Header Section */
header {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: var(--light-text);
    padding: 4rem 2rem;
    text-align: center;
}

header h1 {
    font-size: 3rem;
    margin-bottom: 0.5rem;
    font-weight: 700;
}

header h2 {
    font-size: 1.5rem;
    font-weight: 400;
    opacity: 0.9;
    margin-bottom: 1rem;
}

header .meta {
    font-size: 1.1rem;
    margin-top: 1rem;
    display: flex;
    justify-content: center;
    gap: 2rem;
}

/* Navigation (Optional, simple sticky inner nav if needed, or just sections) */
nav {
    background: #fff;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
    position: sticky;
    top: 0;
    z-index: 100;
    padding: 1rem 0;
    text-align: center;
}

nav a {
    color: var(--primary-color);
    text-decoration: none;
    margin: 0 1rem;
    font-weight: 600;
    text-transform: uppercase;
    font-size: 0.9rem;
}

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

/* Container */
.container {
    max-width: 1000px;
    margin: 0 auto;
    padding: 2rem;
}

/* Sections */
section {
    margin-bottom: 4rem;
}

section h2 {
    font-size: 2rem;
    color: var(--primary-color);
    margin-bottom: 1.5rem;
    padding-bottom: 0.5rem;
    border-bottom: 2px solid var(--secondary-color);
}

p {
    margin-bottom: 1rem;
    text-align: justify;
}

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

.avatar-placeholder, .avatar {
    width: 100px;
    height: 100px;
    border-radius: 50%;
    margin: 0 auto 1rem auto;
    display: block;
    object-fit: cover;
}

.avatar-placeholder {
    background-color: #e0e0e0;
    background-image: linear-gradient(135deg, #e0e0e0 25%, #f5f5f5 25%, #f5f5f5 50%, #e0e0e0 50%, #e0e0e0 75%, #f5f5f5 75%, #f5f5f5 100%);
    background-size: 20px 20px;
}

.speaker-card {
    background: var(--light-bg);
    padding: 1.5rem;
    border-radius: 8px;
    box-shadow: 0 2px 5px rgba(0,0,0,0.05);
    transition: transform 0.2s;
    text-align: center;
}

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

.speaker-card h3 {
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.speaker-card h3 a {
    text-decoration: none;
    color: inherit;
}

.speaker-card h3 a:hover {
    color: var(--secondary-color);
}

.speaker-card .bio {
    font-size: 0.9rem;
    color: #555;
    text-align: left;
}

/* Schedule */
.schedule-table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 1rem;
}

.schedule-table th, .schedule-table td {
    padding: 1rem;
    text-align: left;
    border-bottom: 1px solid #ddd;
}

.schedule-table th {
    background-color: var(--light-bg);
    font-weight: 600;
}

.schedule-table tr:hover {
    background-color: #fafafa;
}

.time-col {
    white-space: nowrap;
    width: 150px;
    font-weight: 600;
    color: var(--secondary-color);
}

/* Organizers */
.organizer-list {
    list-style: none;
    display: flex;
    flex-wrap: wrap;
    gap: 1.5rem;
    justify-content: center;
}

.organizer-item {
    text-align: center;
}

.organizer-item a {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 600;
    font-size: 1.1rem;
}

.organizer-item a:hover {
    color: var(--secondary-color);
}

/* Footer */
footer {
    background: var(--primary-color);
    color: #fff;
    text-align: center;
    padding: 2rem;
    margin-top: 4rem;
}

footer p {
    text-align: center;
    font-size: 0.9rem;
    opacity: 0.8;
}

/* Responsive */
@media (max-width: 768px) {
    header h1 { font-size: 2rem; }
    .meta { flex-direction: column; gap: 0.5rem; }
    nav a { display: inline-block; margin: 0.5rem; }
}