.history_panel {
    height: 100%;
    overflow: hidden;
}

.scroller {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
}

.history_panel ul {
    padding: 0;
    margin: 0;
}

.history_panel li {
    padding: 10px 15px;
    list-style: none;
}

.undo_list li {
    background-color: hsl(0, 0%, 94%);
    border-top: 1px solid hsl(0, 0%, 100%);
    border-bottom: 1px solid hsl(0, 0%, 85%);
}

.redo_list li {
    background-color: hsl(199, 71%, 79%);
    border-top: 1px solid hsl(0, 0%, 100%);
    border-bottom: 1px solid hsl(0, 0%, 85%);
}