Me and a friend were having a discussion on button design and came across the hover-state of the outline buttons of Marvel.
I believe this is not the right approach as an outline button is designed that way for a reason. When an outline button is no longer outline, I believe users might experience a loss of context.
As an alternative, I'd choose for an outline button to have an increase of color vibrancy on the outline as a hover state.
What do you think the hover state of an outline-button should look like?