:root {
    --primary-blue: #007bff;
    --dark-blue: #0056b3;
    --light-blue: #e7f1ff;
    --success-green: #28a745;
    --gray-bg: #f8f9fa;
    --text-dark: #334155;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
}

body {
    background-color: #f1f5f9;
    color: var(--text-dark);
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
}

/* Card Header - Xanh dương Gradient nhẹ, tinh tế */
.card {
    border: none;
    border-radius: 16px;
    box-shadow: var(--shadow);
}

.card-header {
    background: white !important; /* Đổi sang nền trắng cho sang */
    border-bottom: 1px solid #e2e8f0 !important;
    padding: 1.25rem !important;
}

.card-header h5 {
    color: var(--primary-blue);
    font-weight: 700;
}

/* NÚT THÊM DANH MỤC CHA - Thiết kế lại hoàn toàn */
.btn-header {
    background-color: var(--primary-blue);
    color: white;
    border: none;
    border-radius: 8px;
    padding: 8px 16px;
    font-weight: 600;
    font-size: 0.875rem;
    transition: all 0.2s;
    box-shadow: 0 4px 12px rgba(0, 123, 255, 0.2);
}

.btn-header:hover {
    background-color: var(--dark-blue);
    transform: translateY(-1px);
    box-shadow: 0 6px 15px rgba(0, 123, 255, 0.3);
    color: white;
}

/* Danh mục cha */
.category-parent {
    background: white;
    border: 1px solid #f1f5f9;
    border-radius: 12px;
    padding: 12px 16px;
    margin-bottom: 12px;
}

.parent-info {
    display: flex;
    align-items: center;
    gap: 12px;
}

.icon-box {
    width: 40px;
    height: 40px;
    background: var(--light-blue);
    color: var(--primary-blue);
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.1rem;
}

/* Nút cộng nhỏ */
.btn-plus {
    width: 32px;
    height: 32px;
    border: 1.5px solid #d1d5db;
    border-radius: 8px;
    color: #9ca3af;
    background: transparent;
    transition: all 0.2s;
}

.btn-plus:hover {
    border-color: var(--success-green);
    color: var(--success-green);
    background: #f0fdf4;
}

/* Danh mục con */
.category-child-container {
    margin-left: 20px;
    padding-left: 20px;
    border-left: 2px solid #f1f5f9;
    margin-top: 8px;
}

.category-child {
    background: #f8fafc;
    padding: 8px 12px;
    border-radius: 8px;
    margin-bottom: 4px;
    font-size: 0.9rem;
    display: flex;
    align-items: center;
    gap: 8px;
}

/* Responsive cho Mobile */
@media (max-width: 576px) {
    .card-header {
        padding: 1rem !important;
    }
    .btn-header {
        padding: 6px 12px;
        font-size: 0.8rem;
    }
}