body {
  margin: 0 auto;
  padding: 0;
  width: 50rem;
}

a.button {
  background-color: #e9e9ed;
  border-radius: 4px;
  border: 1px solid black;
  font-size: 12px;
  padding: 4px 8px;
  text-decoration: none;
}
a:visited.button {
  color: unset;
}

.container {
  display: flex;
  flex-direction: column;
}

.container .row {
  display: flex;
  margin: 0.6rem 0;
  justify-content: center;
}

.row label,
.row .key {
  flex: 1 0 20%;
  margin-right: 1rem;
  text-align: right;
}
.row input,
.row .value {
  flex: 1 1 80%;
}
.row.error {
  color: tomato;
}