Both have three games in the app. The first is where there is a flask and the student chooses the correct graph that would show the rate at which the flask is filled. If you get it right it shows as green, otherwise it is red. In addition, you can select animate so you can see the graph actually being drawn as the flask is filled.
I find it rather cool.
The final section is called Doodle. The idea behind the part of game that I played was to watch the movement and then draw the line for the x and for the y. Once you've drawn the lines, you can check your work to see how close you were.
I really like the app because it shows some very real applications of linear graphing. It allows the students to work at their own pace and get to work on transferring the theory into practical. Tomorrow I'll share something fantastic I found to help use these apps and others from the Center for Algebraic Thinking.