+.SH INTERACTION
+If you run this program in standalone mode you can rotate the polytope
+by dragging the mouse while pressing the left mouse button. This
+rotates the polytope in 3D, i.e., around the wx, wy, and wz planes.
+If you press the shift key while dragging the mouse with the left
+button pressed the polytope is rotated in 4D, i.e., around the xy, xz,
+and yz planes. To examine the polytope at your leisure, it is best to
+set all speeds to 0. Otherwise, the polytope will rotate while the
+left mouse button is not pressed.