index.css

body {
    animation: colorcycle 40s infinite ease;
    font-family: "Comic Sans MS", sans-serif;
}

@keyframes colorcycle {
    0% {
        background: red;
        color: white;
    }
    25% {
        background: yellow;
        color: black;
    }
    50% {
        background: blue;
        color: white;
    }
    75% {
        background: green;
        color: white;
    }
    100% {
        background: red;
        color: white;
    }
}

.card {
    background-color: white;
    max-width: 420px;
    margin: 50px auto 50px auto;
    box-shadow: 2px 2px 2px black;
    text-align: center;
    padding: 25px;
    border-radius: 25px;
    color: black;
}

.button {
    padding: 25px;
    margin: 25px;
    box-shadow: 2px 2px 2px black;
    animation: colorcycle 40s infinite;
    border-radius: 25px;
    color: white;
    display: inline-block;
    text-decoration: none;
    font-weight: bold;
}

.left {
    text-align: left;
}

#flying-cat {
    position: fixed;
    z-index: -1;
}