Let a *line* in three-dimensional space be given by two points A and B. The coordinates of these two
points (in a Cartesian coordinate system) can be varied by using the input fields at the top right; integers from −5 to +5
are allowed. The buttons in the lower part of the panel are for controlling the projection direction.

The app draws a projection of the coordinate system and the line (black); a vector that determines the direction of the line
is represented by the violet arrow. Below the drawing a *vector equation* (with parameter λ) is given.