Screen

Screen is the base class that all other Screens derive from.

Screen Types
In later versions of StepMania (5.0, sm-ssc), Screens are categorized into one of four types:
 * Attract
 * GameMenu
 * Gameplay
 * SystemMenu

Metrics
Every Screen will have these metrics:

Lua Bindings
(Only valid in StepMania 4 alphas, StepMania 5, and sm-ssc)