A correction: :active applies while the mouse is being clicked, not just after, as this Sitepoint tutorial explains:
This pseudo-class matches any element that’s in the process of being activated. It would apply, for instance, for the duration of a mouse-click on a link, from the point at which the mouse button’s pressed down until the point at which it’s released again. The pseudo-class does not signify a link to the active, or current, page—that’s a common misconception among CSS beginners.
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