body {
  font-family: Arial, sans-serif;
  margin: 20px;
  width: 50%;
}
textarea {
  width: 100%;
  height: 150px;
}
button {
  margin: 10px 0;
  padding: 10px;
  cursor: pointer;
}
.valid {
  color: green;
}
.invalid {
  color: red;
}

.highlight {
  font-weight: bold;
  color: red;
}