Our aim in this chapter is to consider the interplay between the design of digital technologies
and activities that utilize those technologies for learning mathematics. We focus
on geometry, covering both Euclidean and co-ordinate geometry in two and three dimensions,
and non-Euclidean geometries such as spherical, hyperbolic and fractal geometry.
The reason for considering this span of geometries is to capture key aspects of how the
use of digital technologies can and does shape the mathematical activity of the user.