details {
    padding: 0.5em 0.5em 0;
    margin-top: 0.5em;
}

summary {
    font-weight: bold;
    margin: -0.5em -0.5em 0;
    padding-left: 1em;
}

summary.wave {
    font-size: larger;
}

details[open] {
    border: 1px solid #aaa;
    border-radius: 4px;
    padding-bottom: 1em;
}

details[open] input {
    margin-left: 3em;
}

details[open] summary {
    margin-bottom: 0.5em;
}

input[type=submit] {
    margin: 3em;
}

.error {
    color: red;
}