Configure is a dynamic geometry environment that supports topological transformations and investigations of plane figures.
"Arrow", "Draw", "Erase", "Scissor", "Rotate", and "Scale" do just what you'd expect.
"Glue" to glue endpoints, and "Toggle" to toggle between an arc and a segment.
Revert from any tool back to dragging by clicking in the white space.
What's the big idea? Topological equivalence.
Two shapes are alike if each can be transformed into the other.
Transformations involve bending and stretching, but not breaking or gluing. Only dragging and toggling are permitted.
Use transformations to build groups of shapes that are alike. Then identify the property that shapes in each group have in common.
Related Research Publications
Greenstein, S. (2014) Making Sense of Qualitative Geometry: The Case of Amanda. Journal of Mathematical Behavior, 36, 73-94.