Hi, thank you for your reply. With that solution when I scroll from the first section indeed it is being blocked from playing but that is not my intention.
I've corrected my codepen to visualise problem. https://codepen.io/spacemind/pen/vYmvLmY
When I open page at section #s4 and scroll top to section #s2 I can see that animation has been already played instead only when I reach to that section so it fills my viewpoint.
It is hard to explain on codepen but here is visual explanation:
I'm starting on load of page here:
Scrolling top to section S2