.collapsible {
    color: white;
    cursor: pointer;
    width: 100%;
    outline: none;
    display: flex;
}

.collapsible::after {
    content: " + ";
    padding: 0 10px;
    height: auto;
    display: table;
    color: #555;
    font-weight: bold;
}

.collapsible:hover {
    background-color: #999;
}

.collapsible:hover::after {
    color: #fff;
}

.collapsible.active::after {
    content: " - ";
}

.content {
    padding: 0 18px;
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.2s ease-out;
    background-color: #f1f1f1;
}