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

body {
    background: #0a0a0a;
    color: #e0e0e0;
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    padding: 20px;
}

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

header {
    text-align: center;
    margin-bottom: 60px;
    padding: 40px 20px;
}

h1 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 10px;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.subtitle {
    color: #888;
    font-size: 1.1rem;
}

.controls {
    background: #121212;
    padding: 30px;
    border-radius: 12px;
    margin-bottom: 40px;
    border: 1px solid #222;
}

.search-box {
    width: 100%;
    padding: 15px 20px;
    background: #1a1a1a;
    border: 1px solid #333;
    border-radius: 8px;
    color: #e0e0e0;
    font-size: 1rem;
    margin-bottom: 20px;
    transition: all 0.3s ease;
}

.search-box:focus {
    outline: none;
    border-color: #667eea;
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

.filters {
    display: flex;
    flex-wrap: wrap;
    gap: 15px;
    margin-bottom: 20px;
}

.filter-group {
    flex: 1;
    min-width: 200px;
}

.filter-label {
    display: block;
    color: #999;
    font-size: 0.85rem;
    margin-bottom: 8px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

select {
    width: 100%;
    padding: 12px;
    background: #1a1a1a;
    border: 1px solid #333;
    border-radius: 8px;
    color: #e0e0e0;
    font-size: 0.95rem;
    cursor: pointer;
    transition: all 0.3s ease;
}

select:focus {
    outline: none;
    border-color: #667eea;
}

.stats {
    display: flex;
    justify-content: space-between;
    padding: 15px 0;
    color: #888;
    font-size: 0.9rem;
}

.paper-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
    gap: 25px;
    margin-bottom: 40px;
}

.paper-card {
    background: #121212;
    border: 1px solid #222;
    border-radius: 12px;
    padding: 25px;
    transition: all 0.3s ease;
    position: relative;
    overflow: hidden;
    text-decoration: none;
    display: block;
    color: inherit;
}

.paper-card:hover {
    border-color: #667eea;
    transform: translateY(-5px);
    box-shadow: 0 10px 30px rgba(102, 126, 234, 0.2);
}

.paper-card.completed {
    border-color: #10b981;
    opacity: 0.7;
}

.paper-card.completed::after {
    content: '✓';
    position: absolute;
    top: 15px;
    right: 15px;
    width: 30px;
    height: 30px;
    background: #10b981;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-weight: bold;
}

.paper-number {
    display: inline-block;
    background: #667eea;
    color: white;
    padding: 4px 12px;
    border-radius: 6px;
    font-size: 0.8rem;
    font-weight: 600;
    margin-bottom: 15px;
}

.paper-title {
    font-size: 1.2rem;
    font-weight: 600;
    margin-bottom: 12px;
    color: #fff;
    line-height: 1.4;
}

.paper-description {
    color: #aaa;
    font-size: 0.95rem;
    margin-bottom: 15px;
    line-height: 1.5;
}

.paper-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 15px;
}

.tag {
    background: #1a1a1a;
    color: #888;
    padding: 5px 12px;
    border-radius: 6px;
    font-size: 0.8rem;
    border: 1px solid #2a2a2a;
}

.tag.mandatory {
    background: #991b1b;
    color: #fca5a5;
    border-color: #991b1b;
}

.difficulty {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 8px 14px;
    border-radius: 6px;
    font-size: 0.85rem;
    font-weight: 500;
}

.difficulty.beginner {
    background: #064e3b;
    color: #6ee7b7;
}

.difficulty.intermediate {
    background: #78350f;
    color: #fcd34d;
}

.difficulty.advanced {
    background: #991b1b;
    color: #fca5a5;
}

.phase-header {
    margin: 60px 0 30px;
    padding-bottom: 15px;
    border-bottom: 2px solid #667eea;
}

.phase-title {
    font-size: 1.8rem;
    font-weight: 600;
    color: #667eea;
    margin-bottom: 5px;
}

.phase-description {
    color: #888;
    font-size: 1rem;
}

.no-results {
    text-align: center;
    padding: 60px 20px;
    color: #666;
}

.open-icon {
    position: absolute;
    bottom: 15px;
    right: 15px;
    color: #667eea;
    font-size: 1.2rem;
}

@media (max-width: 768px) {
    h1 {
        font-size: 2rem;
    }

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

    .filters {
        flex-direction: column;
    }
}