style.css

*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
  }
  html,body{
    display: grid;
    height: 100%;
    place-items: center;
    background: #000;
  }
  .center{
    display: flex;
    text-align: center;
    align-items: center;
    justify-content: center;
  }
  .outer{
    position: relative;
    margin: 0 50px;
    background: #111;
  }
  .button{
    height: 70px;
    width: 220px;
    border-radius: 50px;
  }
  .outer button, .outer span{
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
  }
  .outer button{
    background: #111;
    color: #f2f2f2;
    outline: none;
    border: none;
    font-size: 20px;
    z-index: 9;
    letter-spacing: 1px;
    text-transform: uppercase;
    cursor: pointer;
  }
  .button button{
    height: 60px;
    width: 210px;
    border-radius: 50px;
  }
  .outer span{
    height: 100%;
    width: 100%;
    background: inherit;
  }
  .button span{
    border-radius: 50px;
  }
  .outer:hover span:nth-child(1){
    filter: blur(7px);
  }
  .outer:hover span:nth-child(2){
    filter: blur(14px);
  }
  .outer{
    background: linear-gradient(#14ffe9, #ffeb3b, #ff00e0);
    animation: rotate 1.5s linear infinite;
  }
  @keyframes rotate {
    0%{
      filter: hue-rotate(0deg);
    }
    100%{
      filter: hue-rotate(360deg);
    }
  }
  @media (max-width: 640px){
    .center{
      flex-wrap: wrap;
      flex-direction: column;
    }
    .outer{
      margin: 50px 0;
    }
  }