/* CSS Variables */
:root {
    --color-primary: #2563eb;
    --color-primary-dark: #1d4ed8;
    --color-secondary: #0f172a;
    --color-accent: #06b6d4;
    --color-bg: #ffffff;
    --color-bg-alt: #f8fafc;
    --color-text: #334155;
    --color-text-light: #64748b;
    --color-border: #e2e8f0;
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    --font-mono: 'JetBrains Mono', monospace;
    --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
    --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.1);
    --radius: 8px;
    --max-width: 1200px;
}

/* Reset & Base */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-sans);
    color: var(--color-text);
    line-height: 1.6;
    background: var(--color-bg);
}

a {
    color: var(--color-primary);
    text-decoration: none;
    transition: color 0.2s;
}

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

/* Container */
.container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 24px;
}

/* Navigation */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background: rgba(255,255,255,0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--color-border);
    z-index: 1000;
}

.nav-content {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 24px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 64px;
}

.nav-logo {
    font-weight: 700;
    font-size: 1.25rem;
    color: var(--color-secondary);
}

.nav-links {
    display: flex;
    list-style: none;
    gap: 32px;
}

.nav-links a {
    color: var(--color-text);
    font-size: 0.9rem;
    font-weight: 500;
}

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

/* Hero */
.hero {
    background: linear-gradient(135deg, var(--color-secondary) 0%, #1e3a5f 100%);
    color: white;
    padding: 160px 24px 100px;
    text-align: center;
}

.hero-content {
    max-width: 800px;
    margin: 0 auto;
}

.hero-venue {
    font-size: 0.9rem;
    text-transform: uppercase;
    letter-spacing: 2px;
    opacity: 0.8;
    margin-bottom: 16px;
}

.hero h1 {
    font-size: 4rem;
    font-weight: 700;
    margin-bottom: 16px;
    letter-spacing: -1px;
}

.hero-subtitle {
    font-size: 1.5rem;
    opacity: 0.9;
    margin-bottom: 24px;
}

.hero-details {
    font-size: 1.1rem;
    margin-bottom: 40px;
}

.hero-separator {
    margin: 0 16px;
    opacity: 0.5;
}

.hero-cta {
    display: flex;
    gap: 16px;
    justify-content: center;
    flex-wrap: wrap;
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 14px 28px;
    border-radius: var(--radius);
    font-weight: 600;
    font-size: 1rem;
    transition: all 0.2s;
    cursor: pointer;
    border: none;
}

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

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

.btn-secondary {
    background: rgba(255,255,255,0.1);
    color: white;
    border: 1px solid rgba(255,255,255,0.3);
}

.btn-secondary:hover {
    background: rgba(255,255,255,0.2);
    color: white;
}

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

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

/* Sections */
.section {
    padding: 80px 24px;
}

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

.section h2 {
    font-size: 2.5rem;
    color: var(--color-secondary);
    margin-bottom: 40px;
    text-align: center;
}

.section-intro {
    text-align: center;
    font-size: 1.1rem;
    color: var(--color-text-light);
    max-width: 700px;
    margin: -20px auto 40px;
}

/* About Section */
.about-grid {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 60px;
    align-items: start;
}

.about-text p {
    margin-bottom: 16px;
    font-size: 1.05rem;
}

.about-goals {
    background: var(--color-bg-alt);
    padding: 32px;
    border-radius: var(--radius);
    border-left: 4px solid var(--color-primary);
}

.about-goals h3 {
    font-size: 1.25rem;
    margin-bottom: 16px;
    color: var(--color-secondary);
}

.about-goals ul {
    list-style: none;
}

.about-goals li {
    padding: 8px 0;
    padding-left: 24px;
    position: relative;
}

.about-goals li::before {
    content: "→";
    position: absolute;
    left: 0;
    color: var(--color-primary);
}

/* Dates Grid */
.dates-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 24px;
}

.date-card {
    background: white;
    padding: 24px;
    border-radius: var(--radius);
    text-align: center;
    box-shadow: var(--shadow-md);
}

.date-label {
    font-size: 0.9rem;
    color: var(--color-text-light);
    margin-bottom: 8px;
}

.date-value {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--color-secondary);
}

.date-note {
    font-size: 0.85rem;
    color: var(--color-text-light);
    margin-top: 4px;
}

/* Challenges */
.challenges-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(400px, 1fr));
    gap: 32px;
    margin-bottom: 60px;
}

.challenge-card {
    background: var(--color-bg-alt);
    padding: 40px;
    border-radius: var(--radius);
    border: 1px solid var(--color-border);
}

.challenge-icon {
    font-size: 3rem;
    margin-bottom: 16px;
}

.challenge-card h3 {
    font-size: 1.5rem;
    color: var(--color-secondary);
    margin-bottom: 16px;
}

.challenge-card p {
    margin-bottom: 16px;
}

.challenge-impact {
    font-style: italic;
    color: var(--color-text-light);
    font-size: 0.95rem;
}

/* Partners */
.partners {
    background: white;
    padding: 40px;
    border-radius: var(--radius);
    box-shadow: var(--shadow-sm);
}

.partners h3 {
    text-align: center;
    margin-bottom: 32px;
    color: var(--color-secondary);
}

.partners-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 40px;
}

.partner {
    text-align: center;
}

.partner strong {
    display: block;
    font-size: 1.25rem;
    margin-bottom: 8px;
    color: var(--color-secondary);
}

/* Speakers */
.speaker-card {
    background: white;
    padding: 32px;
    border-radius: var(--radius);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--color-border);
}

.speaker-card.keynote {
    border: 2px solid var(--color-primary);
    margin-bottom: 32px;
    text-align: center;
}

.speaker-badge {
    display: inline-block;
    background: var(--color-primary);
    color: white;
    padding: 4px 16px;
    border-radius: 20px;
    font-size: 0.85rem;
    font-weight: 600;
    margin-bottom: 16px;
}

.speaker-card h3 {
    font-size: 1.5rem;
    color: var(--color-secondary);
    margin-bottom: 8px;
}

.speaker-title {
    color: var(--color-primary);
    font-weight: 500;
    margin-bottom: 8px;
}

.speaker-talk {
    font-style: italic;
    color: var(--color-text-light);
    margin-bottom: 12px;
}

.speaker-bio {
    font-size: 0.95rem;
    color: var(--color-text);
}

.speakers-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 24px;
}

/* Schedule */
.schedule-table {
    background: white;
    border-radius: var(--radius);
    overflow: hidden;
    box-shadow: var(--shadow-md);
}

.schedule-row {
    display: grid;
    grid-template-columns: 150px 1fr;
    border-bottom: 1px solid var(--color-border);
}

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

.schedule-header {
    background: var(--color-secondary);
    color: white;
    font-weight: 600;
}

.schedule-time,
.schedule-event {
    padding: 16px 24px;
}

.schedule-time {
    font-family: var(--font-mono);
    font-size: 0.9rem;
    background: var(--color-bg-alt);
    border-right: 1px solid var(--color-border);
}

.schedule-header .schedule-time {
    background: transparent;
    border-right-color: rgba(255,255,255,0.2);
}

.schedule-break {
    background: #fef3c7;
}

.schedule-break .schedule-time {
    background: #fde68a;
}

.schedule-social {
    background: #dbeafe;
}

.schedule-social .schedule-time {
    background: #bfdbfe;
}

/* CFP */
.cfp-requirements {
    background: white;
    padding: 32px;
    border-radius: var(--radius);
    margin-bottom: 40px;
    box-shadow: var(--shadow-sm);
}

.cfp-requirements h3,
.cfp-topics h3,
.cfp-ethics h3 {
    font-size: 1.25rem;
    color: var(--color-secondary);
    margin-bottom: 16px;
}

.cfp-requirements ul {
    list-style: none;
}

.cfp-requirements li {
    padding: 8px 0;
    padding-left: 24px;
    position: relative;
}

.cfp-requirements li::before {
    content: "•";
    position: absolute;
    left: 8px;
    color: var(--color-primary);
}

.topics-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 24px;
    margin-bottom: 40px;
}

.topic {
    background: white;
    padding: 24px;
    border-radius: var(--radius);
    box-shadow: var(--shadow-sm);
}

.topic h4 {
    color: var(--color-primary);
    margin-bottom: 12px;
    font-size: 1.1rem;
}

.topic ul {
    list-style: none;
    font-size: 0.95rem;
}

.topic li {
    padding: 4px 0;
    padding-left: 16px;
    position: relative;
}

.topic li::before {
    content: "–";
    position: absolute;
    left: 0;
    color: var(--color-text-light);
}

.cfp-ethics {
    background: white;
    padding: 24px;
    border-radius: var(--radius);
    border-left: 4px solid var(--color-accent);
}

/* Organizers */
.organizers-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 24px;
}

.organizer-card {
    background: var(--color-bg-alt);
    padding: 24px;
    border-radius: var(--radius);
    border: 1px solid var(--color-border);
}

.organizer-card h3 {
    color: var(--color-secondary);
    margin-bottom: 4px;
}

.organizer-title {
    color: var(--color-primary);
    font-weight: 500;
    margin-bottom: 8px;
}

.organizer-role {
    display: inline-block;
    background: var(--color-primary);
    color: white;
    padding: 2px 10px;
    border-radius: 12px;
    font-size: 0.8rem;
    margin-right: 8px;
}

/* Affiliations */
.affiliations {
    display: flex;
    justify-content: center;
    gap: 40px;
    margin-top: 32px;
    flex-wrap: wrap;
}

.affiliation-logo {
    height: 80px;
    object-fit: contain;
}

/* Footer */
footer {
    background: var(--color-secondary);
    color: rgba(255,255,255,0.8);
    padding: 40px 24px;
    text-align: center;
}

footer a {
    color: var(--color-accent);
}

footer p {
    margin: 4px 0;
}

/* Responsive */
@media (max-width: 768px) {
    .nav-links {
        display: none;
    }

    .hero h1 {
        font-size: 2.5rem;
    }

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

    .about-grid {
        grid-template-columns: 1fr;
        gap: 32px;
    }

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

    .schedule-row {
        grid-template-columns: 100px 1fr;
    }

    .schedule-time,
    .schedule-event {
        padding: 12px 16px;
        font-size: 0.9rem;
    }
}