:root {
    --primary: #0f172a;
    --accent: #3b82f6;
    --accent-light: #dbeafe;
    --accent-dark: #1e40af;
    --bg: #ffffff;
    --surface: #f8fafc;
    --text: #334155;
    --text-light: #94a3b8;
    --border: #e2e8f0;
    --radius: 12px;
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    color: var(--text);
    background: var(--bg);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
}

/* Hero */
.hero {
    background: url('title.png') center center / cover no-repeat;
    color: white;
    padding: 5rem 2rem 4rem;
    text-align: center;
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: 0; left: 0; right: 0; bottom: 0;
    background: rgba(15, 23, 42, 0.7);
    pointer-events: none;
}

.hero > * { position: relative; z-index: 1; }

.hero .badge {
    display: inline-block;
    background: rgba(59,130,246,0.2);
    border: 1px solid rgba(59,130,246,0.3);
    color: #93c5fd;
    padding: 0.35rem 1rem;
    border-radius: 100px;
    font-size: 0.8rem;
    font-weight: 500;
    letter-spacing: 0.05em;
    text-transform: uppercase;
    margin-bottom: 1.5rem;
}

.hero h1 {
    font-size: 2.8rem;
    font-weight: 700;
    line-height: 1.15;
    margin-bottom: 1rem;
    letter-spacing: -0.03em;
}

.hero h1 span {
    background: linear-gradient(135deg, #60a5fa, #a78bfa);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero .subtitle {
    font-size: 1.15rem;
    font-weight: 300;
    color: #cbd5e1;
    max-width: 600px;
    margin: 0 auto 2rem;
}

.hero-meta {
    display: flex;
    justify-content: center;
    gap: 2rem;
    flex-wrap: wrap;
    font-size: 0.9rem;
    color: #94a3b8;
}

.hero-meta div {
    display: flex;
    align-items: center;
    gap: 0.4rem;
}

.hero-meta svg {
    width: 16px;
    height: 16px;
    stroke: #60a5fa;
    fill: none;
    stroke-width: 2;
    stroke-linecap: round;
    stroke-linejoin: round;
}

/* Nav */
nav {
    background: rgba(255,255,255,0.95);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border);
    padding: 0.9rem 2rem;
    text-align: center;
    position: sticky;
    top: 0;
    z-index: 100;
}

nav a {
    color: var(--text);
    text-decoration: none;
    margin: 0 1rem;
    font-size: 0.85rem;
    font-weight: 500;
    transition: color 0.2s;
}

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

/* Main */
main {
    max-width: 820px;
    margin: 0 auto;
    padding: 0 2rem;
}

section {
    padding: 4rem 0;
}

section + section {
    border-top: 1px solid var(--border);
}

h2 {
    font-size: 1.6rem;
    font-weight: 700;
    color: var(--primary);
    margin-bottom: 0.4rem;
    letter-spacing: -0.02em;
}

.section-lead {
    color: var(--text-light);
    font-size: 1rem;
    margin-bottom: 2rem;
}

p { margin-bottom: 1rem; }

.highlight-box {
    background: linear-gradient(135deg, var(--accent-light), #ede9fe);
    border-radius: var(--radius);
    padding: 1.5rem 2rem;
    margin: 1.5rem 0;
    font-size: 1.1rem;
    font-weight: 500;
    color: var(--primary);
}

/* Topic cards */
.topic-group {
    margin-bottom: 1.5rem;
}

.topic-group h3 {
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--accent-dark);
    margin-bottom: 0.6rem;
}

.topic-group ul {
    list-style: none;
    margin: 0;
}

.topic-group li {
    padding: 0.45rem 0 0.45rem 1.2rem;
    position: relative;
    font-size: 0.95rem;
}

.topic-group li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0.85rem;
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--accent);
}

/* Dates */
.dates-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
    gap: 1rem;
    margin-top: 1.5rem;
}

.date-card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1.2rem 1.4rem;
    transition: border-color 0.2s;
}

.date-card:hover {
    border-color: var(--accent);
}

.date-card .label {
    font-size: 0.8rem;
    font-weight: 500;
    color: var(--text-light);
    text-transform: uppercase;
    letter-spacing: 0.04em;
    margin-bottom: 0.3rem;
}

.date-card .date {
    font-size: 1rem;
    font-weight: 600;
    color: var(--primary);
}

.date-note {
    margin-top: 1rem;
    font-size: 0.85rem;
    color: var(--text-light);
}

/* Submission */
.format-cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 1rem;
    margin: 1.5rem 0;
}

.format-card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1.5rem;
}

.format-card h4 {
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--primary);
    margin-bottom: 0.5rem;
}

.format-card p {
    font-size: 0.9rem;
    margin-bottom: 0;
    color: var(--text);
}

/* Schedule */
.schedule-item {
    display: flex;
    gap: 1.5rem;
    padding: 0.9rem 0;
    border-bottom: 1px solid var(--border);
    align-items: baseline;
}

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

.schedule-time {
    font-family: 'Inter', monospace;
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--accent);
    min-width: 50px;
}

.schedule-title {
    font-size: 0.95rem;
}

.schedule-item.break {
    background: var(--surface);
    margin: 0 -1rem;
    padding: 0.9rem 1rem;
    border-radius: 8px;
    border-bottom: none;
}

/* Speakers */
.speaker-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
    gap: 1rem;
    margin-top: 1.5rem;
}

.speaker-card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1.3rem;
    text-align: center;
    transition: transform 0.2s, box-shadow 0.2s;
}

.speaker-card:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0,0,0,0.08);
}

.speaker-avatar {
    width: 48px;
    height: 48px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--accent-light), #ede9fe);
    margin: 0 auto 0.8rem;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    font-size: 0.85rem;
    color: var(--accent-dark);
}

.speaker-card .name {
    font-weight: 600;
    font-size: 0.9rem;
    color: var(--primary);
}

.speaker-card .affiliation {
    font-size: 0.8rem;
    color: var(--text-light);
    margin-top: 0.15rem;
}

/* Organizers */
.organizer-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(230px, 1fr));
    gap: 0.8rem;
    margin-top: 1.5rem;
}

.organizer-item {
    display: flex;
    align-items: center;
    gap: 0.8rem;
    padding: 0.8rem 1rem;
    background: var(--surface);
    border-radius: 8px;
}

.organizer-dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: var(--accent);
    flex-shrink: 0;
}

.organizer-item .name {
    font-weight: 600;
    font-size: 0.9rem;
    color: var(--primary);
}

.organizer-item .affiliation {
    font-size: 0.8rem;
    color: var(--text-light);
}

/* Footer */
footer {
    background: var(--primary);
    color: #94a3b8;
    text-align: center;
    padding: 2.5rem 2rem;
    margin-top: 2rem;
    font-size: 0.85rem;
}

footer a {
    color: #60a5fa;
    text-decoration: none;
}

footer a:hover { text-decoration: underline; }

/* Confirmation Banner */
.confirmation-banner {
    background-color: #fff3cd;
    color: #856404;
    padding: 1rem;
    margin-top: 2rem;
    border: 1px solid #ffeeba;
    border-radius: var(--radius);
    text-align: center;
    font-weight: 500;
}

@media (max-width: 640px) {
    .hero { padding: 3rem 1.5rem 2.5rem; }
    .hero h1 { font-size: 1.8rem; }
    .hero-meta { gap: 1rem; }
    nav a { margin: 0 0.5rem; font-size: 0.8rem; }
    main { padding: 0 1.2rem; }
    section { padding: 2.5rem 0; }
    .speaker-grid { grid-template-columns: repeat(2, 1fr); }
}