A design application uses metadata-based techniques (e.g., runtime reflection) to examine class metadata of design objects. A key object is provided by a programmer of a graphical design application to generically animate properties of design objects in one or more animation frames. Using runtime reflection or other metadata techniques, the key object finds properties of each design object and updates specified property values for animated display in one or more animation frames. A key set object is provided to group multiple key objects into a sequence of key frames along a timeline. In this manner, a programmer can provide a small amount of support program code (e.g., a key class and a key set class) that can be associated with selected design objects at runtime of the design application in order to allow an animation designer to decide which design objects and which properties to animate.