html{  background: linear-gradient(133deg, #e0e0e0, #f6f6f6);
    background-size: 200px 100px;
    animation: AnimationName 50s ease infinite; }
@keyframes AnimationName {    
    0%{background-position:0% 50%}    
    50%{background-position:100% 50%}    
    100%{background-position:0% 50%}
}