html {
    margin: 0;
    padding: 0;
    height: 100%;
}
.hero {
    position: fixed;
    z-index: -1;
    inset: 0;
    width: 100%;
    height: auto;
    background-color: gray;
    background-image: url("../smile-background.jpg");
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
    overflow: hidden;
}
footer {
    position: relative;
    bottom: 0;
    left: 0;
    margin: 0;
    background: rgba(0, 0, 0, 0.9);
    border-top: 3px solid purple;
    color: white;
    text-align: center;
    padding: 15px 0;
    width: 100%;
}
footer p{
    font-size: 10px;
}