/* Main Category Section */
.main-category-section {
    margin-bottom: 50px;
}

.category-header {
    padding: 30px 0 20px;
    border-bottom: 3px solid #10b981;
    margin-bottom: 30px;
}

.category-header .category-icon {
    font-size: 40px;
    color: #10b981;
    margin-right: 15px;
    vertical-align: middle;
}

.category-header .category-title {
    display: inline-block;
    font-size: 32px;
    font-weight: 700;
    color: #1e293b;
    margin: 0;
}

.category-header .category-description {
    font-size: 16px;
    color: #64748b;
    margin-top: 10px;
    margin-bottom: 0;
}

/* Sub-Topics Accordion */
.sub-topics-section {
    background: #f8fafc;
    padding: 30px;
    border-radius: 12px;
    margin-top: 40px;
    margin-bottom: 40px;
}

.sub-topics-title {
    font-size: 24px;
    font-weight: 700;
    color: #1e293b;
    margin-bottom: 25px;
}

.sub-topics-title i {
    color: #10b981;
    margin-right: 10px;
}

.sub-topic-card {
    background: white;
    border: 1px solid #e2e8f0;
    border-radius: 8px;
    margin-bottom: 12px;
    overflow: hidden;
    transition: all 0.3s ease;
}

.sub-topic-card:hover {
    box-shadow: 0 4px 12px rgba(0,0,0,0.08);
}

.sub-topic-header {
    background: white;
}

.sub-topic-button {
    width: 100%;
    padding: 18px 20px;
    background: none;
    border: none;
    text-align: left;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 15px;
    transition: all 0.3s ease;
}

.sub-topic-button:hover {
    background: #f8fafc;
}

.sub-topic-button.collapsed .sub-topic-icon {
    transform: rotate(0deg);
}

.sub-topic-button:not(.collapsed) .sub-topic-icon {
    transform: rotate(180deg);
}

.sub-topic-number {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 32px;
    height: 32px;
    background: linear-gradient(135deg, #10b981 0%, #059669 100%);
    color: white;
    border-radius: 50%;
    font-weight: 700;
    font-size: 14px;
    flex-shrink: 0;
}

.sub-topic-title-text {
    flex: 1;
    font-size: 16px;
    font-weight: 600;
    color: #1e293b;
}

.sub-topic-icon {
    color: #10b981;
    transition: transform 0.3s ease;
    font-size: 14px;
}

.sub-topic-body {
    padding: 25px 20px 25px 67px;
    border-top: 1px solid #e2e8f0;
    background: #fafbfc;
}

/* Responsive */
@media (max-width: 768px) {
    .category-header .category-title {
        font-size: 24px;
    }
    
    .sub-topic-body {
        padding: 20px 15px;
    }
}

/* Sub-Topics as Clickable Links */.sub-topics-list { display: flex; flex-direction: column; gap: 12px; }.sub-topic-link-card { display: flex; align-items: center; gap: 15px; padding: 20px; background: white; border: 2px solid #e2e8f0; border-radius: 8px; text-decoration: none; transition: all 0.3s ease; }.sub-topic-link-card:hover { border-color: #10b981; box-shadow: 0 4px 12px rgba(16, 185, 129, 0.15); transform: translateX(5px); text-decoration: none; }.sub-topic-content { flex: 1; }.sub-topic-link-title { font-size: 18px; font-weight: 600; color: #1e293b; margin: 0 0 5px 0; }.sub-topic-summary { font-size: 14px; color: #64748b; margin: 0; }.sub-topic-arrow { color: #10b981; font-size: 18px; transition: transform 0.3s ease; }.sub-topic-link-card:hover .sub-topic-arrow { transform: translateX(5px); }.sidebar-subtopics-list { list-style: none; padding-left: 20px; margin: 8px 0 0 0; }.sidebar-subtopics-list li { margin: 0; padding: 0; }.sidebar-subtopics-list li a { display: block; padding: 8px 12px; font-size: 13px; color: #64748b; border-left: 2px solid #e2e8f0; text-decoration: none; transition: all 0.2s ease; }.sidebar-subtopics-list li a:hover { color: #10b981; border-left-color: #10b981; background: #f8fafc; }.sidebar-subtopics-list li.active a { color: #10b981; font-weight: 600; border-left-color: #10b981; background: #f0fdf4; }