title: How to create skill tree?
body: <p>I would like to create a skill tree for my own and a community usage. I have data in format like below:</p>
  
  <pre><code>skill_1 [description etc.] requires: none
  skill_2 [...] requires: skill_1
  skill_3 [...] requires: skill_1, skill_2
  skill_4 [...] requires: skill_1 OR skill_2
  </code></pre>
  
  <p>(data format from Civilization 5 units promotion)</p>
  
  <p>now i want to change those informations into graphic, tree-like structure. Something like: <a href="http://nick.gladius.org/projects/planner/index.html" rel="noreferrer">skill tree image</a></p>
  
  <p>The main problem I have is that connections between skills tangle and I would recive mess instead of clear, helpful picture, when I add those skills just one by one. Is there any (sort?) algorithm to prevent (or minimalise) crossing connections? Or I have to possition them mannually in a graphic program? </p>