.form-group {
  margin-bottom: 0px;
}

input, textarea {
  width: 100%;
  padding: 8px;
  box-sizing: border-box;
}

.error {
  color: red;
  font-size: 0.9em;
  display: block;
  margin-top: 5px;
}

input.invalid, textarea.invalid {
  border: 2px solid red;
}

input.valid, textarea.valid {
  border: 2px solid green;
}