No classes today, long weekend, spent basically the whole thing rewriting the experiment-logging system from scratch. The old version worked fine, technically, but every new feature I wanted to bolt on made it uglier, and I finally hit the point where fixing the foundation was faster than continuing to patch around it. Six hours in one sitting, which is more consecutive focus than I usually manage. New version is smaller, faster, and — bonus — actually readable if I have to come back to it in six months, unlike the thing it replaced. Small, satisfying kind of day. No breakthroughs, just good, unglamorous engineering.