.redpack {
  height: 450px;
  background: #A5423A;
  width: 300px;
  left: 0;
  top: 0;
  border-radius: 10px;
  margin: 0 auto;
}
.topcontent {
    height: 300px;
    border: 1px solid #BD503A;
    background-color: #BD503A;
    border-radius: 10px 10px 50% 50% / 10px 10px 15% 15%;
    box-shadow: 0px 4px 0px -1px rgba(0,0,0,0.2);
}
#redpack-open {
    width: 100px;
    height: 100px;
    border: 1px solid #FFA73A;
    background-color: #FFA73A;
    border-radius: 50%;
    color: #fff;
    font-size: 20px;
    display: inline-block;
    margin-top: -50px;
    box-shadow: 0px 4px 0px 0px rgba(0, 0, 0, 0.2);
}

<p class=&#39;redpack&#39;>
  <!--  红包的顶部盖子 -->
  <p class="topcontent"></p>
  <!-- 拆红包的按钮 -->
  <p id="redpack-open"></p>
</p>