After using depth testing, the transparency became quite strange

[ouzhou]

I drew two circles. To increase the z-index of the first circle, I tried to modify its depth, but it seems that the background color has become strange.

https://codepen.io/ouzhou-the-bashful/pen/YPKRbXz

I tried adjusting the blend parameters, but I haven't found a solution yet.
The desired outcome is to elevate the hierarchy like CSS does, while ensuring that background colors can be properly overlaid