html, body {
    margin: 0;
    padding: 0;
    border: 0;
    background-color: grey;
}
footer {
    border-top: 2px solid black;
    font-weight: bold;
}
footer > center > p {
    margin: 0;
}
body {
    display: flex;
    flex-direction: column;
    height: 100vh;
    width: 100vw;
}
#content {
    flex-grow: 1;
    max-width: 70vw;
    margin: auto;
    display: flex;
    flex-direction: column;
}
form {
    display: flex;
    flex-direction: column;
    max-width: 40vw;
    align-self: center;
}
form > label {
    margin-top: 6px;
}

input:invalid {
    border: 2px dotted red;
}

bold {
    font-weight: bold;
    color: red;
    background-color: black;
}

:root {
    --primary: #efefef;
    --text-primary: #222;
}

@media (prefers-color-scheme: dark) {
    :root {
        --primary: #222;
        --text-primary: #eee;
    }
}

@media screen and (max-width: 500px) {
    #content {
        max-width: unset;
    }
}