body {
    display: flex;
}

#sidebar {
    width: 250px;
    transition: width 0.3s;
}

#sidebar.collapsed {
    width: 0;
    overflow: hidden;
}

#content {
    flex-grow: 1;
    transition: margin-left 0.3s;
}

#content.full-width {
    margin-left: 0;
}