html{
    font-size: 16px;
    margin: 0;
    padding: 0;
}
body {
    margin: 0;
    height: 100%;
    font-family: Arial, Helvetica, sans-serif;
}  

/* navbar */
.topnav {
    overflow: hidden;
    background-color: #7F00FF;
}
.topnav a {
    float: left;
    display: block;
    color: #f2f2f2;
    text-align: center;
    margin: 0 1rem 0 1rem;
    padding: 14px 16px;
    text-decoration: none;
    font-size: 22px;
} 
.topnav a:hover {
    background-color: #ddd;
    color: black;
} 
.topnav .icon {
    display: none;
} 

/* content */
/* background */
.content{
    width: 100%;
    height:500px;
    background-image:url(library.jpg);
    background-attachment: fixed;
    background-size: cover; 
    padding:1rem 2rem;
}
/* slogan */
.slogan{
    font-size: 3rem;
    margin: 3rem 25% ;
    color: yellow; 
    text-align: center;
    font-weight: bold;
    text-shadow: 3px 3px 2px rgb(45,45,45); 
}
/* buttons */
.dropbtn {
    background-color: #DBDBDB;
    color: #7F00FF;
    padding: 1rem;
    font-size: 1.5rem;
    font-weight: bold;
    width: 100%;
    border-radius: 5px;
    box-shadow: 2px 2px 2px rgb(45, 45, 45);
  }
  
  .dropdown {
    width: 22%;
    margin:1rem 5% ;
    position: relative;
    display: inline-block;
    }
  
  .dropdown-content {
    display: none;
    position: absolute;
    background-color: #dbdbdb;
    width: 70%;
    margin: 0 15%;
    box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
    z-index: 1;
  }
  
  .dropdown-content a {
    color: black;
    padding: 12px 16px;
    font-size: 1.2rem;
    text-decoration: none;
    text-align: center;
    display: block;
  }
  
  .dropdown-content a:hover {background-color: #F1f1f1; color: #7F00FF;}
  
  .dropdown:hover .dropdown-content {display: block;}
  
  .dropdown:hover .dropbtn {background-color:#f2f2f2;}


  /* subjects */
  .in{
    margin-top: -10px;
    text-align: center;
  }
  .sub{
    margin-top: -40px;
    width: 100%;
  }
  .sub.sub_ul{
    width: 100%;
  }
  .sub li{
    text-decoration: none;
    list-style: none; 
    display: inline-block;
    height: 50px;
    width: 25%;
    margin: 20px 3%;
  }
  .sub .sub_ul h1{
    font-size: 2rem;
    text-align: center; 
    height: 50px;
    color: #7F00FF;
    background-color: #DBDBDB;
    border-radius: 20px;
  }
  .sub a h1:hover{
    color: #9c42f6;
    background-color: #ddd;
    border: 1px  solid red;
     border-radius: 25px;
  }

  .credit{
    width: 100%;
    color: white;
    background-color: #1c2331;
    border: 1px solid black;
    border-bottom: 1px solid #fff;
  }
  .credit .h2{
    margin-top: 10px;
    text-align: center;
  }
  .credit h5{
    display: inline-block;
    min-width: 120px;
    margin: 20px 0 20px 9%;
    font-size: 1rem;
    color: yellow;
    text-align: center;
  }

@media screen and (max-width:900px) and (min-width:441px){
  .credit h5{
    font-size: 1rem;
    margin-left:13%;
  }
}
@media screen and (max-width:440px){
  .credit h5{
    font-size: 0.9rem;
    margin-left:12%;
    margin-bottom: 10px;
  }
}