<div class="container">
  <div class="main">I'm fatfish, 6 years of programming experience, like front-end, writing
    and making friends,looking forward to becoming good friends with you.</div>
  <div class="footer">rule</div>
</div>

* {
  margin: 0;
  padding: 0;
}

.container {
  height: 100vh;
  /* Key Style */
  display: flex;
  flex-direction: column;
  justify-content: space-between;
}

.main {
  /* Key Style */
  flex: 1;
  background-image: linear-gradient(
    45deg,
    #ff9a9e 0%,
    #fad0c4 99%,
    #fad0c4 100%
  );
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
}

.footer {
  padding: 15px 0;
  text-align: center;
  color: #ff9a9e;
  font-size: 14px;
}