I should have added in my message to Ed that my 9th grade daughter learned how to use sketchpad this past year and incorporated in into her science fair project very nicely. She was investigating whether or not she could predict how many interior regions would be formed if she started with a rectangular region and drew intersecting lines across the region. It took a while but she learned that no more than two lines could intersect at a given point and finally if she really wanted to know the exact number of lines, each new line drawn had to cur all previously drawn lines. With a little help from her algebra I teacher, her TI 82 and the sketchpad she put together a very nice project. (Not too bad for a kid who hated math in the 5th grade and is considered on level for her age group. Not only did she have an excited algebra I teacher, she also had a pretty proud mom.