I think the quality of content is good. Its a hard concept for many high schoolers to understand. Thinking about it reverse is an interesting and different way to come at this type of problem. As someone who considers themselves good wtih Math, I would tend to want to skip ahead and pick answers to just "get done" with it, since the program allowed me to do that. If its used as an introductory activity and I had no prior knowledge , I would find this extremely confusing...not enough visuals for me as someone who learns that way. I was getting lost in all the words, with no way to remember what problem I was on( unless you are requiring them to write it down as a grade).
It was very easy to use, with no major technical difficulties. There was one problem that talked about solving for "y" but I never saw a "y" in the question. I think it was the one that said -9x+5=53. Assuming this was new material to me, I would have been very frustrated.
I think graphics would have added to the presentation and understanding for all learners.