&gt; But what do you mean by &quot;low level tech tree&quot;? None of those words are in the article.<p>The title of the submission is taken directly from the email subject.<p><a href="http:&#x2F;&#x2F;starfighters.io&#x2F;" rel="nofollow">http:&#x2F;&#x2F;starfighters.io&#x2F;</a> has a great intro to what this is, made by community members &#x27;patio11 and &#x27;tptacek.