I want container queries

Currently, elements can only be sized based on the size of the viewport. However, there's often the need to size an element based on the size of its parent container irrespective of the viewport size.
The use cases are really well documented and Resize Observer isn't sufficient to address them.

One challenge in this area is that implementing container queries could cause infinite loops if the size of child elements alter the size of the container which then changes the size of the child elements and so on.