Let's look at a constant controller in more detail.
The top two buttons control the constant. Pushing the up arrow will increase a from 1 to 1.1. Pushing the down arrow will decrease it to 0.9.
The step buttons allow you to control how much a is changed each time. At the moment the step is 0.1. Pushing the up arrow will increase it to 0.25. Pushing the down arrow will decrease it to 0.05.
You can also type new values for a and Step directly into to the boxes.
We will discuss Families of Curves and Animations later in the next sections.