Yeah. Here is a surprisingly readable article on all the supported features and design decisions of JPEG XL: https://arxiv.org/abs/2506.05987
The format is designed to be as general as possible, potentially replacing many common (JPEG, GIF, PNG) and professional image formats.
For example, JPEG XL supports pages (e.g. for comic books), layers (with variable frame sizes, positions and blend modes) and timed animations.
That was indeed surprisingly readable and very in-depth at the same time. Thanks for sharing!
I wish they had kept the support for progressive decoding of animations just like FLIF had but I guess they had to draw the complexity line somewhere.