.collapsible {
    background-color: #eee;
    color: #444;
    cursor: pointer;
    padding: 18px;
    width: 100%;
    border: none;
    text-align: left;
    outline: none;
    font-size: 15px;
}
.collapsible:hover {
    background-color: #ccc;
}
.collapsible span {
    font-weight: bold;
}
.collapsible i {
    float: right;
}
.collapsible_content {
    max-height: 0;
    background-color: #f1f1f1;
    overflow: hidden;
    transition: max-height 0.2s ease-out;
    padding: 15px;
}