body {
    font-family: Arial, Helvetica, sans-serif;
    padding: 10px;
    background-color: rgb(220, 220, 220);
}

.header {
    text-align: center ;
    /* border: 2px solid darkblue; */
    padding: 5px 0px;
    border-radius: 20px;
    margin-bottom: 20px;
    background-image: linear-gradient(45deg,#19264c,#9ebeca);
    color: whitesmoke;
    transition: 2s;
}
.header:hover {
    opacity: 0.8;
    box-shadow: 5px 5px 10px black;
    transition: 0.5s;
}

.topnav {
    background-image: linear-gradient(30deg,#03202e,#073d66);  
    overflow: hidden;
    border-radius: 10px;
}

.topnav a{
    color: whitesmoke;    
    text-decoration: none;
    float: left;
    display: block;
    padding: 5px 15px;
}

.topnav a:hover {
    background-color: #ddd;
    color: black;
}

.container::after {
    clear:both;
    display: table;
}

.card {
    padding: 20px;
    margin-top: 20px;
    background-color: white;
    border-radius: 10px;
}

.footer {
    background-image: radial-gradient(circle,#000,#555);
    color: whitesmoke;
    text-align: center;
    padding: 10px;
    margin-top: 20px;
    border-radius: 10px;
}
.footer a {
    text-decoration: underline;
    color: white
}

@keyframes example {
    0% {color:#FF0000}
    35% {color:#FF0000}
    65% {color:#0000FF}
    100% {color:#00FF00}
}

.secret {
    /* color:black; */
    animation-name: example;
    animation-duration: 2s;
    animation-iteration-count: infinite;
    animation-direction: alternate;
}