# Concepts

cast
  The cast is the list of objects that take part in an animation.
object
  The available object types are Line, Rectangle, Arc, Ellipse, Pixmap, String, Point, Filled Rectangle, Filled Arc and Filled Ellipse.
script
  Every object has a script, which is a list of ticks telling the object where it should move and when.
tick
  A tick is a structure containing all properties of an object at a certain point in time.
property
  The available properties are position (x and y), size (width and height), visibility, color, font and string.
duration
  The number of milliseconds the animation will take.
delta
  The number of milliseconds between each frame. A smaller delta can make the movement smoother but also present the CPU with a heavier load.
now
  The "current time" in the animation. For every frame, the position and size of each object is calculated at the time now. If no tick matches now exactly in the object's script, the values are interpolated from the surrounding ticks.