body {
  margin: 0;
  width: 100vw;
  height: 100vh;
  background-image:url("https://magazine-cf.techacademy.jp/wp-content/uploads/2021/03/20220916/laptop_small.jpg");
  background-repeat: no-repeat;
  background-position:50% 50%;
  background-size:contain;
}

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