效果图：
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Verb</title>
<style>
.center {
position: absolute;
margin: auto;
top: 0;
right: 0;
bottom: 0;
left: 0;
width: 100px;
height: 100px;
background-color: transparent;
border-radius: 50%;
box-shadow: 25px 10px 0px 0px blue;
}
</style>
</head>
<body>
<div class="center"></div>
</body>
</html>
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Verb</title>
<style>
.heart {
position: absolute;
margin: auto;
top: 0;
right: 0;
bottom: 0;
left: 0;
background-color: pink;
height: 50px;
width: 50px;
transform: rotate(-45deg);
}
.heart::after {
background-color: pink;
content: "";
border-radius: 50%;
position: absolute;
width: 50px;
height: 50px;
top: 0px;
left: 25px;
}
.heart::before {
background-color: pink;
border-radius: 50%;
position: absolute;
width: 50px;
height: 50px;
top: -25px;
left: 0px;
content: '';
}
</style>
</head>
<body>
<div class="heart"></div>
</body>
</html>