My blog background needs a little extra flair - I want it to subtly move every time the page is scrolled, creating a 3D effect. To better explain my vision, I've included an illustration:
How can I achieve this? For example, if the posts on my blog are moved down by 50%, I'd like the background to only move down by 25%. Essentially, the background should move half as much as the posts do. Any advice would be greatly appreciated! Thank you!