body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  margin: 0;
  padding: 0;
  text-align: center;
  background: linear-gradient(-45deg, #0ea5e9, #8b5cf6, #ec4899, #f59e0b);
  background-size: 400% 400%;
  animation: gradient 15s ease infinite;
  color: white ;
  padding-top: 50px;
}
 
@keyframes gradient {
  0%   { background-position: 0% 50%; }
  50%  { background-position: 100% 50%; }
  100% { background-position: 0% 50%; }
}

a {
    text-decoration: none;
    background-color: gray;
    padding: 10px;
    border-radius: 5px;
    color: white;
}

a:hover{
   
    background-color: white;
    color: gray;
    transition: 0.5s;
}
@media (max-width:640px) {

    body {
        background-size: cover;
        background-position: top;
        background-position: center;
        margin: 0px;
        padding: 50px 5%;
        background-image: url(science-fiction-1674554_640.jpg);
       height: 90vh;

    }

}

@media (min-width:640px) and (max-width:1280px)

{

    body{
        background-size: cover;
        background-position: top;
        background-position: center;
        background-image: url(science-fiction-1674554_1280.jpg);
       height: 90vh;
    }
}    

@media (min-width:1280px) and (max-width:1920px)

{

    body{
        background-size: cover;
        background-position: top;
        background-position: center;
        background-image: url(science-fiction-1674554_1920.jpg);
        height: 90vh;
        
    }

}