Not a video, but here for nostalgic purposes. I used to call this system the Sweet Spot Density Indicator (SSDI) because everyone always tried to find the sweet spot. However, when research proved there was no detectable sugar in coffee I decided the system was more about avoiding sour and bitter, and that Density Assisted Extraction (DAE ) spoke more to the two parts of the system, measuring density to get a better starting extraction, and using changes in density to assist with extraction adjustments. The sweet spot was gone, removed from the front page. It did take me quite a while to create in visio on the train journey to work each morning. Perhaps that inspired the London Metro Map analogy.