I love the program. Great work. I know, you that a lot.
I have a few suggestions for the graph screen that would make it a lot easier to use (at least for me). On my TI-83 there was a ZoomFit function that would fit the zoom values to the graph automatically. I don't know the details, but it was really handy. Also, there was a square setting that would adjust the zoom so that the x and y were equal and the graph wasn't stretched. Also, while the zoom is great the way it is, if you could add a percent zoom also that would be great. Maybe with the same button only use a single tap instead of selecting a box.
I would also like to echo a few others by saying that scripting or programming like dedicated graphing calculators would be wonderful.
Thank you for the program. I use it nearly exclusively.