* {
    box-sizing: border-box;
}

main {
    margin: auto;
    padding: 10px;
    background-color: black;
}

fieldset {
    background-color: gray;
    color: wheat;
    max-width: 600px;
    margin: auto;
    border-radius: 5px;
}
fieldset legend {
    text-align: center;
    font-size: 1.5em;
}
form {
    text-align: center;
}
form input[type="submit"]{
    background-color: black;
    color: wheat;
}