html {
    margin: auto;
    max-width: 72ch;
}
h1, h2, h3, h4, h5, h6 { margin: 1ex 0 }
form {
    display: grid;
    grid-template-columns: max-content 1fr;
}
form label { margin-right: 1ch }
form label:after { content: ":" }
form input { margin-bottom: 1ex }
.error { color: red }