title: How to make a flowchart/diagram using only HTML and CSS
body: <p>I need to make a really complicated diagram for a website, in which the hierarchy will be a bit messy: arrows will go up and down, sometimes an element will point to several others, and sometimes there will be several elements pointing to the same one. I have found <a href="http://thecodeplayer.com/walkthrough/css3-family-tree" rel="noreferrer">this method</a>, but it doesn't allow more than one parent for an element and therefore won't do the trick in this case.</p>
  
  <p>It has to be done in HTML/CSS, because my intention is to add some Javascript to change the content of the blocks dinamically.</p>
  
  <p>This is an example of the level of complexity I need to achieve:
  <img src="https://i.stack.imgur.com/i6hWN.jpg" alt="chart"></p>