<body>
    <button id="foot"><button class="button-os"><a href="#">BUTTON</a></button></button>
</body>

* {
  padding: 0;
  margin: 0;
  box-sizing: border-box;
}

body {
  height: 100vh;
  overflow: hidden;
  display: flex;
  align-items: center;
  justify-content: center;
}

button{
  border: none;
  border-radius: 15px;
  box-shadow: 0 0 8px rgb(207, 207, 207);
}

button:hover{
  border: none;
  padding: 15px;
  border-radius: 15px;
  box-shadow: inset 0 0 8px #f9f8fc;
  } 

 #foot{
  position: relative;
  top: 15px;
  left: 0;
  right: 0;
  bottom: 0;
  margin: auto;
  border: none;
  padding: 15px;
  border-radius: 15px;
  box-shadow: 0 0 8px #d9d4e7;
  width: 200px;
  height: 65px;
  background-color: #d9d4e7;
  animation-duration: 5s;
}

.button-os{
   position: absolute;
    width: 200px;
    height: 65px;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    margin: auto;
    background-color: #f9f8fc;
    border: 2.5px solid #0e172c;
    transition: background-color 2.2s;
    transition-duration: 3s;
    transition: 1.5s;
  }
  
  .button-os:hover{
    position: absolute;
    top: 30px;
    background-color: #fec7d7;
  }
  
  .button-os a{
    font-size: 20px;
    display: block;
    text-decoration: none;
    color:#0e172c;
    transition: 1.5s;
  }
  
  .button-os a:hover{
    letter-spacing: 5px;
  }

External CSS

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External JavaScript

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