.split {
    display: flex;
    flex-direction: row;
    width:100%;
    height:100%;
    z-index: 1;
    /*padding: 30px;
    border: 1px solid;*/
}

.gutter {
    background-color: #eee;
    background-repeat: no-repeat;
    background-position: 50%;
}

    .gutter:hover {
        background-color: #e4e4e4;
        border-left: 1px solid #aaa;
        border-right: 1px solid #aaa;
    }

.gutter.gutter-horizontal {
    background-image: url('data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAeCAYAAADkftS9AAAAIklEQVQoU2M4c+bMfxAGAgYYmwGrIIiDjrELjpo5aiZeMwF+yNnOs5KSvgAAAABJRU5ErkJggg==');
    cursor: col-resize;
}