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This article presents an overview of the Alternate Reality Kit, an animated environment for creating interactive simulations. ARK is built upon a physical-world metaphor: All objects have an image, a position, a velocity, and the ability to experience forces. Users manipulate objects with a mouse-operated "hand," which enables them to carry and throw objects, press buttons, and operate sliders. The interface features are discussed in light of a general user interface tension between literalism and magic. Literal features??defined as those that are true to the interface's metaphor??enhance an interface's learnability. Magical features are defined as those capabilities that deliberately violate the metaphor in order to provide enhanced functionality. Discussion of each ARK feature includes informal observations of early ARK users, and an assessment of the feature's learnability, its usefulness, and its position on the magical-literal axis. Despite ARK's magical features, applications-level users have been trained in a few minutes. Although this article is about ARK, the tension between literalism and magic raises some interesting questions on its own. Some of these questions are presented briefly in the conclusion.