body {
  margin: 0;
  min-height: 100vh;
  background: green url("background.png") repeat;
  font-family: Arial, sans-serif;
}

.page-shell {
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
}

.card {
  width: 350px;
  padding: 20px;
  color: black;
  background: white;
  border: 3px solid black;
}

h1 { margin-top: 0; }
label { display: block; margin: 15px 0 4px; }
input { width: 100%; padding: 6px; box-sizing: border-box; }
button { margin-top: 15px; }
.field-error { min-height: 18px; margin: 3px 0 0; color: red; }
.message { margin-top: 15px; }