下拉菜单中的箭头通常用于提示用户点击以展开菜单。CSS三角形实现这个箭头：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>CSS三角形应用示例 - 下拉菜单箭头</title>
<style>
body {
font-family: Arial, sans-serif;
display: flex;
justify-content: center;
align-items: center;
min-height: 100vh;
background-color: #f9f9f9;
margin: 0;
}
.dropdown {
position: relative;
display: inline-block;
}
.dropdown-button {
padding: 10px 20px;
background-color: #3498db;
color: white;
font-size: 16px;
border: none;
cursor: pointer;
display: flex;
align-items: center;
}
.dropdown-arrow {
margin-left: 10px;
width: 0;
height: 0;
border-left: 5px solid transparent;
border-right: 5px solid transparent;
border-top: 7px solid white;
}
.dropdown-content {
display: none;
position: absolute;
background-color: white;
min-width: 160px;
box-shadow: 0px 8px 16px rgba(0, 0, 0, 0.2);
z-index: 1;
margin-top: 10px;
}
.dropdown-content a {
color: black;
padding: 12px 16px;
text-decoration: none;
display: block;
}
.dropdown-content a:hover {
background-color: #f1f1f1;
}
.dropdown:hover .dropdown-content {
display: block;
}
</style>
</head>
<body>
<div class="dropdown">
<button class="dropdown-button">
下拉菜单
<div class="dropdown-arrow"></div>
</button>
<div class="dropdown-content">
<a href="#">选项 1</a>
<a href="#">选项 2</a>
<a href="#">选项 3</a>
</div>
</div>
</body>
</html>
