title: CSS - Concentric circles
body: <p>I want to create two concentric circles in CSS. The inner one has a specified width compaired to the outer one, e.g. 50%. Those circles should be responsive, they should scale properly for all screens.</p>
  
  <p>How can I do this? I prefer not to use position:absolute, javascript or jQuery. I think it should be possible.</p>
  
  <p>Thanks!</p>
  
  <p><img src="https://i.stack.imgur.com/t90Qb.png" alt="enter image description here"></p>