title: Using ONLY CSS and HTML to set "required" attribute for texarea if radio button is checked
body: <p>I need to add the attribute ":required" on a textarea if a radio button is checked; I cannot use javascript, only css and html, is it possible?</p>
  
  <p>practically if the radio button is checked the text area have to be filled, otherwise it can be empty
  thanks in advance</p>