/* ====================================
   BOOK EXPLORER SECTION (Added)
   ==================================== */
.book-explorer {
    max-width: 1000px;
    margin: 0 auto;
    background: var(--color-white);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-lg);
    border: 1px solid var(--color-gray-100);
    overflow: hidden;
}

.explorer-nav {
    display: flex;
    background: var(--color-gray-50);
    border-bottom: 1px solid var(--color-gray-100);
    overflow-x: auto;
    scrollbar-width: none;
}

.explorer-nav::-webkit-scrollbar {
    display: none;
}

.explorer-tab {
    flex: 1;
    min-width: 200px;
    padding: var(--spacing-md) var(--spacing-lg);
    border: none;
    background: transparent;
    cursor: pointer;
    text-align: left;
    transition: all var(--transition-base);
    border-right: 1px solid var(--color-gray-100);
    position: relative;
    opacity: 0.6;
}

.explorer-tab:last-child {
    border-right: none;
}

.explorer-tab:hover {
    background: rgba(0, 0, 0, 0.02);
    opacity: 0.8;
}

.explorer-tab.active {
    background: var(--color-white);
    opacity: 1;
    box-shadow: 0 -2px 0 var(--color-primary) inset;
}

.tab-number {
    display: block;
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--color-primary);
    margin-bottom: 0.25rem;
}

.tab-title {
    display: block;
    font-weight: 600;
    color: var(--color-gray-900);
    font-size: 1rem;
}

.explorer-content-container {
    padding: var(--spacing-xl);
    min-height: 400px;
}

.explorer-panel {
    display: none;
    animation: fadeIn 0.5s ease;
}

.explorer-panel.active {
    display: block;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.panel-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-2xl);
}

.panel-info h3 {
    font-family: var(--font-display);
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: var(--spacing-md);
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.panel-info p {
    font-size: 1.125rem;
    color: var(--color-gray-600);
    line-height: 1.7;
    margin-bottom: var(--spacing-xl);
}

.panel-stats {
    display: flex;
    gap: var(--spacing-xl);
}

.stat {
    display: flex;
    flex-direction: column;
}

.stat-value {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--color-gray-900);
    line-height: 1;
    margin-bottom: 0.25rem;
}

.stat-label {
    font-size: 0.875rem;
    color: var(--color-gray-500);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    font-weight: 500;
}

.topic-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.topic-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    padding: var(--spacing-md);
    background: var(--color-gray-50);
    border-radius: var(--radius-lg);
    transition: all var(--transition-base);
}

.topic-item:hover {
    background: var(--color-white);
    box-shadow: var(--shadow-md);
    transform: translateX(5px);
}

.topic-icon {
    font-size: 1.5rem;
    display: flex;
    align-items: center;
    justify-content: center;
    width: 48px;
    height: 48px;
    background: var(--color-white);
    border-radius: var(--radius-full);
    box-shadow: var(--shadow-sm);
}

.topic-text strong {
    display: block;
    color: var(--color-gray-900);
    font-weight: 600;
    margin-bottom: 0.125rem;
}

.topic-text small {
    display: block;
    color: var(--color-gray-500);
    font-size: 0.875rem;
}

@media (max-width: 768px) {
    .panel-grid {
        grid-template-columns: 1fr;
        gap: var(--spacing-lg);
    }

    .explorer-nav {
        flex-direction: column;
        border-bottom: none;
    }

    .explorer-tab {
        border-right: none;
        border-bottom: 1px solid var(--color-gray-100);
        padding: var(--spacing-md);
    }

    .explorer-tab.active {
        box-shadow: 2px 0 0 var(--color-primary) inset;
        background: var(--color-gray-50);
    }
}