# Sandbox.UI.PseudoClass

List of CSS pseudo-classes used by the styling system for hover, active, etc.
This acts as a bit-flag.

- Kind: enum
- Namespace: `Sandbox.UI`
- Assembly: `Sandbox.System`
- Modifiers: sealed

## Fields

- [`Active`](/api/Sandbox.UI.PseudoClass/Active): `:active` - A button that is being pressed down.
- [`After`](/api/Sandbox.UI.PseudoClass/After): `:after` - Creates an element on the parent element
- [`Before`](/api/Sandbox.UI.PseudoClass/Before): `:before` - Creates an element on the parent element
- [`Empty`](/api/Sandbox.UI.PseudoClass/Empty): `:empty` - Any element that has no children.
- [`FirstChild`](/api/Sandbox.UI.PseudoClass/FirstChild): `:first-child` - The element is the first element among a group of sibling elements.
- [`Focus`](/api/Sandbox.UI.PseudoClass/Focus): `:focus` - An element with input focus.
- [`Hover`](/api/Sandbox.UI.PseudoClass/Hover): `:hover` - Any element with the mouse cursor hovering over it.
- [`Intro`](/api/Sandbox.UI.PseudoClass/Intro): `:intro` - Present on all elements for their first frame. Useful to start CSS transitions on creation.
- [`LastChild`](/api/Sandbox.UI.PseudoClass/LastChild): `:last-child` - The element is the last element among a group of sibling elements.
- [`None`](/api/Sandbox.UI.PseudoClass/None): No pseudo-class.
- [`OnlyChild`](/api/Sandbox.UI.PseudoClass/OnlyChild): `:only-child` - The element is the only child of their parent element.
- [`Outro`](/api/Sandbox.UI.PseudoClass/Outro): `:outro` - The element has been marked for deletion, and will be deleted once all CSS transitions on it has stopped. Transitions can be started here to gracefully remove the element visually.
- [`Unknown`](/api/Sandbox.UI.PseudoClass/Unknown): Unused.