html {
    width: 100%;
    height: 100%;
}

body {
    background: #c7b9ab;
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
    box-sizing: border-box;
}

#avatar {
    margin-left: auto;
    margin-right: auto;
    box-shadow: 0px 0px 7px black;
    width: 200px;
    height: 200px;
    padding: 0px;
    position: absolute;
    left: 50%;
    top: 30%;
    transform: translate(-50%, -50%);
}

#avatar img {
    width: inherit;
    height: inherit;
}