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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #fff;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Header */
header {
    background: #fff;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    position: fixed;
    width: 100%;
    top: 0;
    z-index: 1000;
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 70px;
}

.logo h1 {
    color: #2563eb;
    font-size: 1.5rem;
    font-weight: 700;
}

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

.nav-links a {
    text-decoration: none;
    color: #666;
    font-weight: 500;
    transition: color 0.3s;
}

.nav-links a:hover {
    color: #2563eb;
}

/* Hero Section */
#hero {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 120px 0 80px;
    text-align: center;
}

#hero h1 {
    font-size: 3rem;
    font-weight: 700;
    margin-bottom: 1rem;
    max-width: 800px;
    margin-left: auto;
    margin-right: auto;
}

.hero-subtitle {
    font-size: 1.25rem;
    opacity: 0.9;
    margin-bottom: 3rem;
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

.hero-stats {
    display: flex;
    justify-content: center;
    gap: 4rem;
    margin-top: 3rem;
}

.stat {
    display: flex;
    flex-direction: column;
    align-items: center;
}

.stat .number {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
}

.stat .label {
    font-size: 1rem;
    opacity: 0.8;
}

/* Sections */
section {
    padding: 80px 0;
}

section h2 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 3rem;
    text-align: center;
    color: #1f2937;
}

/* About Section */
.about-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 4rem;
    align-items: start;
}

.about-text {
    font-size: 1.1rem;
    line-height: 1.8;
}

.about-text p {
    margin-bottom: 1.5rem;
}

.features {
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

.feature {
    background: #f8fafc;
    padding: 1.5rem;
    border-radius: 12px;
    border-left: 4px solid #2563eb;
}

.feature h3 {
    font-size: 1.25rem;
    margin-bottom: 0.5rem;
    color: #1f2937;
}

/* Examples Section */
#examples {
    background: #f8fafc;
}

.examples-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: 2rem;
}

.example-card {
    background: white;
    border-radius: 12px;
    padding: 2rem;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    transition: transform 0.3s, box-shadow 0.3s;
}

.example-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 20px rgba(0,0,0,0.15);
}

.example-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
}

.example-header h3 {
    font-size: 1.25rem;
    color: #1f2937;
}

.difficulty {
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    font-size: 0.875rem;
    font-weight: 500;
}

.difficulty.easy {
    background: #dcfce7;
    color: #166534;
}

.difficulty.medium {
    background: #fef3c7;
    color: #92400e;
}

.difficulty.hard {
    background: #fee2e2;
    color: #991b1b;
}

.task-description {
    margin-bottom: 1.5rem;
}

.task-description h4 {
    font-size: 1rem;
    margin-bottom: 0.5rem;
    color: #374151;
}

.code-block {
    background: #1f2937;
    border-radius: 8px;
    padding: 1rem;
    margin: 1rem 0;
    overflow-x: auto;
}

.code-block pre {
    color: #e5e7eb;
    font-family: 'Monaco', 'Menlo', 'Ubuntu Mono', monospace;
    font-size: 0.875rem;
    line-height: 1.5;
}

.solution {
    margin-top: 1rem;
    padding-top: 1rem;
    border-top: 1px solid #e5e7eb;
}

.solution h4 {
    font-size: 1rem;
    margin-bottom: 0.5rem;
    color: #059669;
}

/* Leaderboard Section */
.leaderboard-table {
    background: white;
    border-radius: 12px;
    overflow: hidden;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
}

table {
    width: 100%;
    border-collapse: collapse;
}

thead {
    background: #f8fafc;
}

th, td {
    padding: 1rem;
    text-align: left;
    border-bottom: 1px solid #e5e7eb;
}

th {
    font-weight: 600;
    color: #374151;
}

tr:hover {
    background: #f9fafb;
}

/* Dataset Section */
#dataset {
    background: #f8fafc;
}

.dataset-info {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 4rem;
}

.categories {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 2rem;
}

.category {
    background: white;
    padding: 1.5rem;
    border-radius: 12px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

.category h4 {
    font-size: 1.125rem;
    margin-bottom: 1rem;
    color: #2563eb;
}

.category ul {
    list-style: none;
}

.category li {
    padding: 0.25rem 0;
    color: #6b7280;
}

.category li:before {
    content: "•";
    color: #2563eb;
    margin-right: 0.5rem;
}

.metric-cards {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.metric-card {
    background: white;
    padding: 1.5rem;
    border-radius: 12px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

.metric-card h4 {
    font-size: 1.125rem;
    margin-bottom: 0.5rem;
    color: #2563eb;
}

.metrics h3 {
    margin-bottom: 1.5rem;
    color: #1f2937;
}

/* Footer */
footer {
    background: #1f2937;
    color: #9ca3af;
    text-align: center;
    padding: 2rem 0;
}

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

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

    .hero-stats {
        flex-direction: column;
        gap: 2rem;
    }

    .about-content {
        grid-template-columns: 1fr;
        gap: 2rem;
    }

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

    .dataset-info {
        grid-template-columns: 1fr;
        gap: 2rem;
    }

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

    table {
        font-size: 0.875rem;
    }

    th, td {
        padding: 0.75rem 0.5rem;
    }
}