Octave Gustave

I am new to Gsap and was wondering how I could tweek this so that there is no more infinite loop. I would like that when you arrive on the page the indexed element is the middle of the number of element and there is an end to the loop, if you get to the element indexed 0 you can't fo further and you don't see the 30th an the 29th and it would be the same at the other extreme : at the 30th you can't see element indexed 0 and 1. I don't really understand the gsap.utils.snap function and everything that goes around the "wrap" concept which seems to be what's doing the trick of setting the timeline to the start if it goes at the end, that I would like to delete.