.sidebar-item.sub-item {
    padding-left: 40px;
    font-size: 10px;
    background: rgba(10,10,10,0.8);
    border-left: 2px solid #9400D3;
}
.sidebar-item.sub-item:hover {
    background: #6a0dad;
}
.sidebar-submenu {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s ease;
}
.sidebar-submenu.open {
    max-height: 2500px;
}
.sidebar-item.toggle-btn::after {
    content: '▼';
    margin-left: auto;
    font-size: 10px;
    transition: transform 0.2s;
}
.sidebar-item.toggle-btn.open::after {
    transform: rotate(180deg);
}