body {
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 0;
    margin: 0;
}
#challenge28 {
    background-color: aqua;
    display: flex;
    width: 100%;
    height: 100%;
    justify-content: center;
    align-items: center;
    animation: change-color 10s linear infinite;
}
#challenge28 h1 {
    color: #fff;
    font-size: 5.5rem;
    text-align: center;
    font-family: 'Courier New', Courier, monospace;
}
@keyframes change-color {
    0% {
        background-color: aqua;
    }
    25% {
        background-color: red;
    }
    50% {
        background-color: blueviolet;
    }
    75% {
        background-color: crimson;
    }
    100% {
        background-color: aqua;
    }
}