One number, two coordinates. In a + bi, a is the real part and b is the imaginary part. The point is (a, b). “Imaginary” is a historical name; it does not mean made-up. The number i is defined by i² = −1.

3D View changes the camera. Real and imaginary coordinates stay on one plane. Drag to tilt it, or choose Flat View to see lengths and right angles without foreshortening. Camera movement never changes your number or your prediction.

This is an introduction using small whole-number coordinates. Complex numbers can also have fractional and other real-valued coordinates. The trails illustrate operations; they are not physical journeys.

Based on the complex-plane representation and arithmetic, with visual precedents from Maths Is Fun, GeoGebra’s arithmetic-and-geometry applet, and Desmos Complex Mode. This game’s prediction missions and artwork were made for SpookyQubits. Learning gains have not been evaluated.