Computer animation has been limited almost exclusively to 2D and 3D. The tools for 3D computer animation have been largely in place for decades and are well-understood. Existing tools for visualizing 4D geometry include minimal animation features. Few tools have been designed specifically for animation of higher-dimensional objects, phenomena, or spaces. None have been designed to be familiar to 3D animators. A general-purpose 4D animation system can be expected to facilitate more widespread understanding of 4D geometry and space, can become the basis for creating unique 3D visual effects, and may offer new insight into 3D animation concepts. We have developed a software package that facilitates general-purpose animation in four spatial dimensions. Standard features from popular 3D animation software have been included and adapted, where appropriate. Many adaptations are trivial; some have required novel solutions. Several features that are possible only in four or more dimensions have been included. The graphical user interface has been designed to be familiar to experienced 3D animators. Keyframe animation is provided by using a set of curves that defines movement in each dimension or rotation plane. An interactive viewport offers multiple visualization methods including slicing and projection. The viewport allows for both manipulation of 4D objects and navigation through virtual 4D space.