This report describes Designer, an interactive tool for assisting with the design of two-dimensional graphic interfaces for instructional systems. The system, which consists of a color graphics interface to a mathematical simulation, provides enhancements to the Graphics Editor component of Steamer (a computer-based training system designed to aid instruction in the domain of propulsion engineering) by allowing nonprogrammer users of the Graphics Editor to create interactive, dynamic views of the simulation. Designer consists of three interrelated processes, an Analyzer, a Critiquer, and a Synthesizer, which are coupled to a domain-dependent knowledge base consisting of design elements; design relationships; techniques for their identification; sets of constraints for establishing a context or style and for critiquing a design; and generative techniques for creating design alternatives. The Analyzer parses a design based on the elements and relationships of the domain and records this information in the knowledge base; the Critiquer uses this information along with domain-based design constraints to indicate where the current design succeeds or fails; and the Synthesizer uses knowledge representing the current state of the design to generate design alternatives within a design style. Subsystems incorporated into the system architecture include Steamer's frame-based knowledge representation facility and an assumption-based truth maintenance system. The text is supplemented with several graphic illustrations. A bibliography, an ICS Technical Report List, and a list of earlier reports by people in the Cognitive Science Lab are also provided. (Author/KM)