1. A method of animating design objects in a graphical animation sequence, the method comprising: presenting design objects selected and positioned by a user in a user interface displayed by a computing device; creating a key set object defining the graphical animation sequence in response to initiating a timeline interface for defining behavior of the design objects in individual frames of the graphical animation sequence; identifying properties of the design objects available for editing by the user using metadata associated with the design objects; displaying a user interface for editing a key frame of the graphical animation sequence; changing design objects in response to editing by the user of one or more identified properties of design objects to be animated in the key frame of the graphical animation sequence; defining a key object corresponding to the key frame; collecting the design objects in the key object corresponding to the key frame, the key objet referencing each changed design object and property change attributable to editing by the user of the one or more identified properties of the design objects to be animated in the key frame of the graphical animation sequence; adding the key object corresponding to the key frame to the key set object defining the graphical animation sequence; recording the graphical animation sequence in animation key frame data based on the key set object and each key object of the key set object; and animating the design objects in the key frame by: initially rendering the design objects in the key frame in accordance with current properties of the design objects from the animation key frame data, building the key set object and the key object corresponding to the key frame from the animation key frame data, identifying active design objects having current properties that change during the key frame and building property setting objects for the current properties of the active design objects that change during the key frame using metadata associated with the key object, iterating through the property setting objects to compute updated property values of the current properties of the active design objects and set the current properties of the active design objects to the updated property values using metadata associated with the active design objects, and providing an updated rendering of the design objects in the key frame in accordance with the updated property values of the current properties of the design objects.