Thumbnail thumbnail preview of YouTube videos?

Question

YouTube

Hello. I'm new to javascript, but I'm trying to script Tampermonkey to view videos by hovering over thumbnails (yes, I'm so lazy that it's hard for me to just click). Here's what I've been able to do so far: https://github.com/sooqua/YouTube-Preview/blob/mas...
Everything works on the main page, in subscriptions and on the search page, but does not work on the video page. The sound plays and I can pan back and forth with the mouse, but the iFrame appears to be transparent. I still see the thumbnail image, but if I delete it, only a white empty space remains (there is no video under it).
What is the reason for this strange behaviour? Maybe my player is conflicting with the player on the video page?

Answer 1

corrected:
playerTag.style.zIndex = '1';