Love the article. Small UX gripe: it took me a while to figure out how to use the gradient sliders. The box at the top looks like a handle, and I was trying to interact with that. But it looks like I have to click the bar to move the box, but there is no visual indicator that the bar itself is a point of interaction other than a cursor change (which is really subtle).
Yeah, I would have considered adding ball with the same styling as the other drag handles at the tip, and remove the ball at the center pivot point. Mimicking the affordance elsewhere, behavior can stay the same as is.
