Curved Spaces is freely distributable under the GNU General Public License.
The current version is available at
www.geometrygames.org/ CurvedSpaces.
Further study
The book The Shape of Space
introduces finite universes to advanced high school students
and beginning university students.
Suitable for self-study as well as classroom use.
Available from
its page at Amazon.com.
The Torus and Klein Bottle Games
let children of all ages have fun while building their intuition
for finite universes in two dimensions. Available for free online.