<form>
  <label for="email">Email Address:</label>
  <input id="email" name="email" type="email" value="na@me@example.com" />

  <label for="secret">Secret Code: (lower case letters)</label>
  <input id="secret" name="secret" type="text" value="test" pattern="[a-z]+" />

  <label for="age">Your age: (18+)</label>
  <input id="age" name="age" type="number" value="5" min="18" />

  <label><input name="tos" type="checkbox" required checked /> - Do you agree to ToS?</label>
</form>

label {
  display: block;
  margin-top: 1em;
}

input:invalid {
  background-color: ivory;
  border: none;
  outline: 2px solid red;
  border-radius: 5px;
}