There are three different levels to Stella, each has its own features and some rely on the other levels. These levels will be called for the purpose of this site, the Authoring Level, the Design Level, and the Equation Level. The Authoring Level allows you to create a user interface for the model you create on the Design Level. The Equation Level allows you to see and manipulate the elements and equations that are created in the Design Level. The Design Level is where you place all of the elements of the model and layout everything.