Drawn close-boxes:

What? What? What? What?

Close-button elements:

Text Text Text

Close-box size and X color are based on the font-size and color properties:

Text Text Text

Text Text Text

Transitions and Animations only work for custom properties in up-to-date Blink-based browsers. So in Chrome, you'll see every parameter of the box transition or animate but in other browsers you'll only see the size and X color animate.

Transition (hover over the button)

Animation