Return to the previous "border" selection

[marcinjahn]

Is your feature request related to a problem? Please describe.
At the beginning, the selection was shown with a border around the selected item. Now, it is a kind of platform below the element. I think the previous design was better, it was more aligned with Gnome design. For example, here's how selection looks like in the Gnome's Settings app:

The other thing that I don't like about the new design is the motion. Changing the selection causes the newly-selected element to slightly go up, which I personally think is not necessary:

The last complain is the fact that the "platform" is quite blurry:

I'm not sure if that was intentional, I think it does not look good.

Describe the solution you'd like
A simple (not blurried) border around the selected element, preferably with an option to select its color via settings.

Describe alternatives you've considered

I think the design should take as much from Adwaita as possible. The default selection in Gnome apps is a border. I think this app should go with that as well.