How do you decide when to make elements darker or lighter on hover?

1. Should hover states be darker or lighter?

Should hover states be darker or lighter?

Darker seems more natural. If anything, a physical button would appear slightly darker when you touch it because your hand is casting a shadow. Lighter (illuminated) might signal that the button is waking up at the moment it's needed, like a fog light, refrigerator light, or moving sidewalk.