kig

Kig, short for KDE Interactive Geometry, is a free, open-source dynamic geometry program designed for exploring Euclidean geometry and for constructing geometric figures. It is part of the KDE Education project and is developed for use in classrooms and self-guided learning. Kig is implemented in C++ using the Qt framework and runs on Linux, Windows, and macOS.

Users can place and manipulate geometric objects such as points, lines, rays, segments, circles, and polygons. The program supports dynamic geometry, so moving a point automatically updates related elements. Construction tools include standard geometric operations, measurements, and transformations such as translation, rotation, reflection, and scaling. Kig also provides facilities for creating and studying loci and envelopes of figures, and for annotating diagrams.

Kig saves diagrams in its own project format with a .kig extension, and can export graphics to common image formats such as SVG and PNG for use in documents. It can also export to other formats compatible with vector graphics workflows. The interface is designed to be lightweight and accessible for classroom use.

Kig is released as free and open-source software under the GNU General Public License, and is available on multiple desktop platforms as part of the KDE Applications suite.