.column {    float: left;    width: 50%;    padding: 10px;}.grid-list:after {    content: "";    display: table;    clear: both;}.btn {    border: none;    outline: none;    padding: 12px 16px;    background-color: #f1f1f1;    cursor: pointer;}.btn:hover {    background-color: #ddd;}.btn.active {    background-color: #666;    color: white;}