[timmins]

While this gesture may not be intuitive, I have to give credit to the initial stage double tap and then the zoom calibration with the vertical slide gesture.

There's another app that has a very similar gesture, Readmill. They allow brightness adjustment with a vertical slide. The downside is the lack of initial gesture to toggle its activation. So, while reading, trying to vertically scroll the page has caused the gesture to activate brightness adjustment. It becomes frustrating.