<div class="container">
  <img src="https://assets.codepen.io/221808/uni.svg" width="150" height="150" class="logo" alt="UNI" />

</div>

.container {
  display: grid;
  place-content: center;
}

/* その他のスタイル */

html,
body {
  height: 100%;
  background-color: #e8faff;
}

body {
  font-family: "游ゴシック Medium", YuGothic, YuGothicM,
    "Hiragino Kaku Gothic ProN", Meiryo, sans-serif;
}

.container {
  height: 100dvh;
}