Popup Border Blends in With Background

[Zeklandia]

The white border around popups blends in with white backgrounds. Either a shadow or a faint line around the outside would easily fix this.

[hdni]

Assuming you mean the Shell popups, the way the Gnome team implemented shadows isn't really convenient to work with. Since Phosphene's popups have an arrow, the shadows end up being ugly or nonsensical. If I removed the arrows, it would be possible, but I'm a stubborn blockhead who thinks that those little triangles make more sense in this case.
I've considered adding a border — that's what I did for my other themes — but didn't do it because it would be inconsistent. All the other windows and popups are simply white, so I felt sheepish to add a border only for the popups, and I don't want to touch the rest because I'm pleased with it. Really, a shadow would be the best solution; that's what I did for the OSD and the notifications, as you've probably noticed.

Though you're right that it's a problem, so I'll leave the issue open and try to implement a solution that I'm pleased with.