/* ═══ Library Specific Styles ═══ */

.library-container {
    max-width: 600px;
    margin: 0 auto;
    padding: var(--space-lg);
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.library-header {
    display: flex;
    flex-direction: column;
    padding-top: var(--space-md);
    margin-bottom: var(--space-sm);
}

.library-header h1 {
    font-family: var(--font-display);
    font-size: 2rem;
    letter-spacing: 0.05em;
}

.subject-card {
    font-size: 0.95em;
    background: var(--surface-color);
    border: 2px solid var(--border-light);
    border-radius: 22px;
    overflow: hidden;
    transition: var(--transition-snappy);
    margin-bottom: 5px;
}

.subject-card:hover {
    border-color: var(--border-dark);
}

.subject-header {
    padding: 13px 17px;
    display: flex;
    align-items: center;
    gap: var(--space-md);
    cursor: pointer;
    transition: background-color 0.2s ease;
}

.subject-header:hover {
    background: var(--bg-color);
}

.subject-icon {
    width: 45px;
    height: 45px;
    border-radius: var(--radius-icon);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 24px;
    border: 2px solid var(--text-primary);
    flex-shrink: 0;
}

.subject-toggle {
    transition: transform 0.4s cubic-bezier(0.25, 1.2, 0.5, 1);
    color: var(--text-secondary);
}

.subject-toggle.open {
    transform: rotate(180deg);
    color: var(--text-primary);
}

.chapter-list {
    display: grid;
    grid-template-rows: 0fr;
    transition: grid-template-rows 0.4s cubic-bezier(0.25, 1.2, 0.5, 1);
    background: var(--surface-color);
}

.chapter-list.open {
    grid-template-rows: 1fr;
}

.chapter-list-inner {
    overflow: hidden;
}

.chapter-item {
    padding: var(--space-md) var(--space-lg);
    display: flex;
    align-items: center;
    gap: var(--space-md);
    border-top: 2px solid var(--border-light);
    transition: background-color 0.2s ease;
}

.chapter-item:hover {
    background-color: var(--bg-color);
}

.chapter-num {
    font-family: var(--font-mono);
    font-weight: 700;
    font-size: 0.85rem;
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    border: 2px solid var(--text-primary);
}

.chapter-item.special {
    background-color: var(--accent-mint);
    border-top: 2px solid var(--border-dark);
}

.subtopic-list {
    background: #fdfdfd;
    padding: 0 var(--space-lg) var(--space-lg);
}

.subtopic-item {
    padding: 8px 12px;
    font-size: 0.9rem;
    color: var(--text-secondary);
    display: flex;
    align-items: center;
    gap: 10px;
}

.subtopic-item::before {
    content: '•';
    color: var(--accent-mint);
    font-weight: bold;
}

.chapter-actions {
    padding: 0 var(--space-lg) var(--space-lg);
    display: flex;
    justify-content: flex-end;
}

.btn-learn {
    background: #000;
    color: #fff;
    border: 2px solid #000;
    font-size: 0.85rem;
    padding: 8px 24px;
    font-weight: 700;
    transition: all 0.1s ease;
    border-radius: 99px;
}

.btn-learn:active,
.btn-learn:hover {
    background: #FFD700;
    /* Vivid Yellow */
    color: #000;
    border: 2px solid #000;
}