C.a.R.– Compass and Ruler (also known as Z.u.L., which stands for the German "Zirkel und Lineal") — is a free and open source interactive geometry app that can do geometrical constructions in Euclidean and non-Euclidean geometry.

The author is René Grothmann of the Catholic University of Eichstätt-Ingolstadt.

Assignments make possible to create Java applets, for a construction exercises.

These applets can be used from the command line using the AppletViewer.

This scientific software article is a stub.