Vivaldi Browser auto-hide webpanel header

/* auto-hide webpanel header */
#panels-container .webpanel-header {
    transform: translateY(0);
    margin-bottom: 0px;
    transition: all .1s 0s !important;
}
#main .mainbar:not(:hover) ~ .inner #panels-container .webpanel-header:not(:hover) {
    transform: translateY(-100%);
    margin-bottom: -41px;
    transition: all .1s 1.5s !important;
}