:root {
    --accent-blue: #3b82f6;
    --accent-purple: #a855f7;
    --accent-gold: #eab308;
    --accent-red: #ef4444;
    --bg-dark: #0a0c10;
    --card-bg: rgba(20, 24, 33, 0.7);
    --border-color: rgba(255, 255, 255, 0.1);
    --text-primary: #ffffff;
    --text-secondary: #94a3b8;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.theory-index-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
    gap: 2rem;
    padding: 2rem 0;
}

.theory-module-card {
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 20px;
    padding: 2rem;
    text-decoration: none;
    color: var(--text-primary);
    display: flex;
    gap: 1.5rem;
    transition: var(--transition);
    backdrop-filter: blur(12px);
    position: relative;
    overflow: hidden;
}

.theory-module-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 4px;
    height: 100%;
    background: var(--accent-blue);
    opacity: 0;
    transition: var(--transition);
}

.theory-module-card:hover {
    transform: translateY(-5px);
    border-color: var(--accent-blue);
    background: rgba(59, 130, 246, 0.05);
    box-shadow: 0 15px 40px rgba(0, 0, 0, 0.3);
}

.theory-module-card:hover::before {
    opacity: 1;
}

.module-number {
    font-size: 2rem;
    font-weight: 800;
    color: var(--accent-blue);
    opacity: 0.5;
    font-family: 'Inter', sans-serif;
    line-height: 1;
}

.module-info h3 {
    font-size: 1.25rem;
    margin-bottom: 0.75rem;
    font-weight: 700;
}

.module-info p {
    color: var(--text-secondary);
    font-size: 0.95rem;
    line-height: 1.6;
    margin-bottom: 1.5rem;
}

.view-link {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--accent-blue);
    transition: var(--transition);
}

.theory-module-card:hover .view-link {
    gap: 0.75rem;
}

.page-header {
    text-align: center;
    margin-bottom: 4rem;
}

.page-tag {
    display: inline-block;
    padding: 0.5rem 1.25rem;
    background: rgba(59, 130, 246, 0.1);
    color: var(--accent-blue);
    border-radius: 100px;
    font-size: 0.85rem;
    font-weight: 700;
    letter-spacing: 0.05em;
    margin-bottom: 1.5rem;
}

.page-title {
    font-size: 3rem;
    font-weight: 800;
    margin-bottom: 1rem;
    background: linear-gradient(135deg, #fff 0%, #94a3b8 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.page-subtitle {
    color: var(--text-secondary);
    font-size: 1.1rem;
    max-width: 600px;
    margin: 0 auto;
}

@media (max-width: 768px) {
    .theory-index-grid {
        grid-template-columns: 1fr;
    }

    .page-title {
        font-size: 2.5rem;
    }
}