Hi, author of the post here. I'll admit I kept the premise simple here in order to provide a more introduction on how to "roll your own" effects without too much overhead.
That is nice, thanks for the link :). It's a pity the touch events don't include finger velocity -- you can confuse the velocity tracker in that example by swiping back and forth quickly before releasing.
Android has a whole bunch of velocity trackers, but they're probably expensive in JS (solve least squares, etc). Code is here: https://github.com/android/platform_frameworks_base/blob/mas...