style.css

body {
    font-family: 'Lato', sans-serif;
    text-align: center;
    color: purple;
    padding:20px;
  }
  
  .overlay {
    height: 100%;
    width: 0;
    position: fixed;
    z-index: 1;
    top: 0;
    left: 0;
    background-color: rgb(0,0,0);
    background-color: rgba(0,0,0, 0.9);
    overflow-x: hidden;
    transition: 0.5s;
  }
  
  .overlay-content {
    position: relative;
    top: 25%;
    width: 100%;
    text-align: center;
    margin-top: 30px;
  }
  
  .overlay a {
    padding: 8px;
    text-decoration: none;
    font-size: 25px;
    color: red;
    display: block;
    transition: 0.3s;
  }
  
  .overlay a:hover, .overlay a:focus {
    color: #f1f1f1;
  }
  
  .overlay .closebtn {
    position: absolute;
    top: 20px;
    right: 45px;
    font-size: 60px;
  }
  
  @media screen and (max-height: 450px) {
    .overlay a {font-size: 20px}
    .overlay .closebtn {
    font-size: 40px;
    top: 15px;
    right: 35px;
    }
  }

  .collapsible {
    background-color: yellow;
    color: purple;
    cursor: pointer;
    padding: 18px;
    width: 100%;
    border: none;
    text-align: center;
    outline: none;
    font-size: 15px;
  }
  
  .active, .collapsible:hover {
    background-color: green;
    color: cyan;
  }
  
  .content {
    padding: 0 18px;
    display: none;
    overflow: hidden;
    background-color: yellow;
    color: purple;
    text-align: center;
  }