.loading {
    z-index: 1051;
    position: fixed;
    top: 0;
    left:-5px;
    width: 100%;
    height: 100%;
    background-color: rgba(0,0,0,0.4);
}
.loading-content {
    position: absolute;
    border: 16px solid #f3f3f3; /* Light grey */
    border-top: 16px solid #3498db; /* Blue */
    border-radius: 50%;
    width: 50px;
    height: 50px;
    top: 40%;
    left:35%;
    animation: spin 2s linear infinite;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

/* ==========================================================================
   사이드바 상위/하위 메뉴 시각적 구분 강화 스타일
   ========================================================================== */

/* 상위 메뉴가 열렸을 때 (menu-open) 상위 메뉴 강조 */
.main-sidebar .nav-sidebar > .nav-item.menu-open > .nav-link:not(.active),
.main-sidebar .nav-sidebar > .nav-item.menu-is-opening > .nav-link:not(.active) {
    background-color: rgba(255, 255, 255, 0.08) !important;
    color: #ffffff !important;
    font-weight: 600;
    border-radius: 4px;
}

/* 하위 메뉴(Treeview) 서브메뉴 컨테이너 영역 */
.main-sidebar .nav-sidebar .nav-treeview {
    background-color: rgba(0, 0, 0, 0.25) !important;
    border-left: 2px solid rgba(255, 255, 255, 0.2) !important;
    border-radius: 0 6px 6px 0;
    margin: 4px 0 6px 0.75rem !important;
    padding: 4px 0 4px 0.35rem !important;
}

/* 하위 메뉴 아이템 링크 */
.main-sidebar .nav-sidebar .nav-treeview > .nav-item > .nav-link {
    font-size: 0.88rem !important;
    padding: 0.45rem 0.65rem !important;
    color: #c2c7d0 !important;
    border-radius: 4px;
    margin-bottom: 2px;
    transition: all 0.15s ease-in-out;
}

/* 하위 메뉴 아이콘: 크기 조정 및 시각적 차별화 */
.main-sidebar .nav-sidebar .nav-treeview > .nav-item > .nav-link > .nav-icon {
    font-size: 0.78rem !important;
    width: 1.15rem !important;
    margin-right: 0.45rem !important;
    opacity: 0.75;
    transition: opacity 0.15s ease-in-out, transform 0.15s ease-in-out;
}

/* 하위 메뉴 마우스 오버(Hover) 효과 */
.main-sidebar .nav-sidebar .nav-treeview > .nav-item > .nav-link:hover {
    background-color: rgba(255, 255, 255, 0.12) !important;
    color: #ffffff !important;
    padding-left: 0.85rem !important;
}

.main-sidebar .nav-sidebar .nav-treeview > .nav-item > .nav-link:hover > .nav-icon {
    opacity: 1 !important;
    color: #60a5fa !important;
    transform: scale(1.1);
}

/* 하위 메뉴 활성화(Active) 상태 */
.main-sidebar .nav-sidebar .nav-treeview > .nav-item > .nav-link.active {
    background-color: #007bff !important;
    color: #ffffff !important;
    font-weight: 600 !important;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.3) !important;
    padding-left: 0.85rem !important;
}

.main-sidebar .nav-sidebar .nav-treeview > .nav-item > .nav-link.active > .nav-icon {
    opacity: 1 !important;
    color: #ffffff !important;
}