*,
*:before,
*:after {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: Helvetica, sans-serif;
}

.container {
  width: 1200px;
  max-width: 100%;
  margin: auto;
  padding: 2rem;
}

main {
  display: flex;
}

form,
.output {
  flex: 1;
  padding: 20px;
}

form {
  border-right: 1px solid black;
}

.output > ul {
  background-color: #eee;
  padding: 20px;
  list-style-type: none;
}

input,
select,
textarea {
  padding: 8px 12px;
  margin-bottom: 10px;
  border: 1px solid #bbb;
}

input.invalid,
select.invalid {
  border-color: red;
}

input:not([type='radio']):not([type='checkbox']),
select,
textarea {
  display: block;
  width: 100%;
}