button{
    margin: 0px auto; 
    text-align: center;
   
}
#button{
    width: 70px;
    height: 50px;
}
body{
    text-align: center;
    font-size: large;
    font-family: Arial, Helvetica, sans-serif;
    
}
#nbclic{
    font-size: xx-large;
}
.shop{
    display: flex;
}
.shop > div{
    flex:1;
}

ul {
    list-style-type: none;
    margin: 0;
    padding: 0;
    overflow: hidden;
    background-color: #000000;
    position: fixed;
    top: 0;
    width: 100%;
    position: -webkit-sticky; /* Safari */
  position: sticky;
  top: 0;
  }
  
  li {
    float: left;
  }
  
  li a {
    display: block;
    color: white;
    text-align: center;
    padding: 14px 16px;
    text-decoration: none;
  }