Some critics of the program would have preferred less money being spent on technology and more money being spent on clean water and "real schools". Some supporters worried about the lack of plans for teaching students. The program was based on constructionism, which is the idea that, if they had the tools, the kids would largely figure out how to do things on their own. Others wanted children to learn the Microsoft Windows operating system, rather than OLPC's lightweight Linux derivative, on the belief that the children would use Microsoft Windows in their careers. Intel's Classmate PC used Microsoft Windows and sold for US$200 to $400.