Z-index Issue

Hi everyone! For the life of me I can't figure out why I can't get my boxes to z-index ontop of the black horizontal line.

The issue starts on line 22 in the css on the code pen. Could anyone give to a hint as to what I'm missing? I've been stuck on this since yesterday.
https://codepen.io/ezekielswanson/pen/rNqOwWO

The boxes are supposed to stack ontop of the line line
it is in the screen shot.
Screen_Shot_2023-04-11_at_9.03.46_PM.png
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