In this theoretical paper, I use an empirically based example to illustrate particular design features of the Learning Through Activity (LTA) design framework and examine the impact of particular design principles. The LTA design framework is based on our elaboration of Piaget's construct of reflective abstraction. The example discussed here, involving the learning of a fraction concept, contains both an unsuccessful attempt, not based on the LTA framework, and a subsequent successful attempt, based on the framework. I use this contrast to make theoretical distinctions with regards to designing for the learning of mathematical concepts. [For the complete proceedings, see ED658295.]