Willy might not agree, and this isn&#x27;t really a criticism, but I think 1.5 simply got out of hand — he did a lot of (much-needed) architectural cleanup that took a long time to complete, but along the way a lot of new features (and subsequent bug fixes) got piled onto the same branch and intermingled with the cleanup work.<p>It&#x27;s one of those &quot;take apart your airplane and put it back together again&quot; projects that one generally shouldn&#x27;t do, though sometimes there is no way around it. If you need to rearrange the whole internal architecture of your engine, you should it do it quickly and not mix it with new work.