Four dimensional viewer
This is a java applet to allow you to visualise motion in 4 dimensions. As it projects the view down into 2 dimensions, there are 2 other dimensions perpendicular to the screen. Pressing the HOME and END keys moves your viewpoint forward and backward in one of these dimensions, PAGEUP and PAGEDOWN in the other. The arrow keys rotate your viewpoint in the appropriate directions. You may need to click the mouse on the applet for it to accept keypresses