Appollos

I have a div in which I have one block and under it 3 child-blocks, on the right side block with text. I need to create an animation in which: when this div in the viewport, I pin it and if user scroll I draw an SVG line from the main block to each child-block, and then we draw a second line (from main to child) we change block with text(simple change content, or toggle class name). Can somebody help with this, please? (Links to the same animation, articles .etc)