body {
      margin: 0;
      height: 100vh;
      width: 100vw; 
      background-image: url('photo/téléchargement (2).jpg');
      background-size: cover; 
      background-position: center;
      transition: background-image 0.3s ease;
    }


  
    .button {
      position: absolute;
      top: 57%;
      left: 71%;
      transform: translate(-50%, -50%); 
      padding: 15px 30px;
      background-color: #000;
      opacity: 0;
      border: none;
      cursor: pointer;
      transition: background-color 0.5s ease; 
      height:200px;
      width:420px;
    }

   
    .button:hover {
      background-color: #444;
    }

   
    .button:hover ~ body {
      background-image: url('photo/téléchargement (1).jpg');