I'm trying to recreate something similar to the following: https://www.apple.com/uk/ipad-mini/design/
When you scroll down on the page it seems to understand that a certain area, when viewed, triggers an animated element. I'm trying to base next steps on this but unsure what to start in. I understand elements of HTML, CSS, DIV Tags and potentially switching on a hidden block when viewed might be the answer. But need advice of the simple trigger element. Java? PHP? CSS?
So when the user scrolls down maybe 30% a hidden element appears or animates. I would animate in adobe edge if that helps.
Any good?