/* 样式重置 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
 
/* 下拉按钮样式 */
.dropbtn {
    background-color: #4CAF50;
    color: white;
    padding: 16px;
    font-size: 16px;
    border: none;
    cursor: pointer;
}
 
/* 下拉内容（默认隐藏） */
.dropdown {
    position: relative;
    display: inline-block;
}
 
.dropdown-content {
    display: none;
    position: absolute;
    background-color: #f9f9f9;
    min-width: 160px;
    box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
    z-index: 1;
}
 
/* 下拉内容链接的样式 */
.dropdown-content a {
    color: black;
    padding: 12px 16px;
    text-decoration: none;
    display: block;
}
 
/* 当鼠标悬停在链接上时改变颜色 */
.dropdown-content a:hover {background-color: #f1f1f1}