A parallax effect has also long been possible with CSS 3D transforms. Here's a demo,[0][1] from the same person who made that CSS 3D FPS a while ago.[2]

[0]: https://www.keithclark.co.uk/articles/pure-css-parallax-webs...

[1]: blog: https://www.keithclark.co.uk/articles/pure-css-parallax-webs...

[2]: https://www.keithclark.co.uk/labs/css-fps/