body {
    font-family: sans-serif;
}
.center {
    display: flex;
    flex-flow: column wrap;
    align-items: center;
}
h1 {
    text-align: center;
}
a {
    color: #778da9;
    font-weight: 500;
    text-decoration: none;
    font-size: 1.4rem;
}
a:link {
    color: #778da9;
}
a:visited {
    color: blueviolet;  
}
a:focus {
    font-size: 1.5rem; 
    transition: 0.2s;
    color: #fff;
    text-decoration: underline;
}
a:hover {
    font-size: 1.5rem;
    color: #fff;
    text-decoration: underline;
    transition: 0.4s;
}
a:active {
    color: #e9ecef;
    text-decoration: underline;
}