Addressing data visualization challenges typically involves applying lessons from visualization theory to inform design and implementation approaches. This process is shaped to a large extent by the availability of tools that are aimed at enabling visualization designers to focus on visualization design rather than on low-level software engineering. Recently, such tools have become powerful enough to be used effectively. We discuss the ideation process informing our design approach and describe the use of Macromedia Flash MX 2004 for the rapid prototyping of a gaze data visualization tool. We highlight selected gaze data visualization ideas to illustrate the most innovative aspects of our design. In particular, we explain our strategy to reveal the underlying mechanisms that produce the summarizing visual constructs and why this is important. We introduce a new technique for visualizing gaze data for dynamic stimuli. The novelty of this approach is that it avoids the traditional frame-by-frame analyses typically carried out for such stimuli.