I have exhausted all my CSS and javascript knowledge and I still could not figure out how they optimize their mobile website so much that it scrolls like a native app, even with images and videos that are occupying most of the viewport, it still scrolls very smooth.

I have exhausted all my CSS and javascript knowledge and I still could not figure out how they optimize their mobile website so much that it scrolls like a native app, even with images and videos that are occupying most of the viewport, it still scrolls very smooth.