This demo displays the straight line given by X(t) = A + tC. To change A or C, type the expression for the desired vector into the appropriate text box in the control window and press Enter. The expression should be of the form (x-coordinate, y-coordinate) (e.g., (1,2)). To move the point X(t0) along the line, use the following keys on the appropriate line in the control window:

[<]: Decrease t0 by one step.
[>]: Increase t0 by one step.
[<<]: Decrease t0 until it reaches its minimum value.
[>>]: Increase t0 until it reaches its maximum value.

By default, the demo shows the point tracing out the curve, so that only part of it is shown. To show the entire curve, check the box "Show entire curve" by clicking on it. Click on the "Show position vector X(t0)" box to show the position vector X(t0) whose components are the coordinates of the point X(t0). To color the curve by t, click on the box "Show Color Spectrum".