console 命令行工具 X clear

console

<body>
  <main>
    <div class="d1"></div>
    <!-- 试着把下面这个容器注释掉 -->
    <div class="d2"></div>
  </main>
</body>

body {
  height:100vh;
}


main {
  background-color: cyan;
  display: flex;
  justify-content: space-between;
  flex-direction: column;
  position: relative;
  height: 100%;
}

main div:only-child {
  background-color: blue;
  margin: auto 0;
}

.d1 {
  width: 100%;
  height: 60px;
  background-color: green;
}

.d2 {
  width: 100%;
  height: 60px;
  background-color: red;
}