This is designed to simulate students playing with base ten blocks. You give a student a number between 0 and 99, and the student has to come up with the correct number of ten blocks and unit blocks.
With this sketch, the student moves the sliders to match the number you give them. When he or she is ready to check, they hit the 'Am I Right' checkbox. The correct number represented by the blocks pops up.
If the student is wrong, moving the sliders and watching the number change may still result in some intuitive understanding of how the representation works. Try it out with your students and let me know how it works.
