CSS ordering issues with absolute positioning in Firefox

Question

I see some inconsistencies with the order property between Firefox and others, but I'm not sure if this is correct.

Basically, I have a page that uses the checkbox hack to open and close the page menu without JS. This means that it’s very important that they are included directly above the element I am switching.

I also have a sidebar, which is located at the bottom of the page for small devices, and on the left for larger ones, so I turn on the sidebar after the content of the page (in my html) and the order: # setting with the request environment.

In another message about elements that are not removed from the normal stream, the order property is proposed.

Firefox seems to still completely ignore the order property as soon as an element with absolute positioning is entered. My thought is that setting these absolutely positioned elements in a lower order (for example: order: -3; ) or something at least lower than other items should do the trick. But not at FF.

Sample code (works in Chrome, not in FF)