+.B \-viscosity float
+This sets the viscosity of the hypothetical fluid through which the control
+points move; the default is 1, meaning no resistance. Values higher than 1
+aren't interesting; lower values cause less motion.
+
+One interesting thing to try is
+.EX
+attraction -viscosity 0.8 -points 75 \\
+ -mouse -geometry =500x500
+.EE
+Give it a few seconds to settle down into a stable clump, and then move
+the mouse through it to make "waves".
+.TP 8
+.B \-mouse
+This will cause the mouse to be considered a control point; it will not be
+drawn, but it will influence the other points, so you can wave the mouse
+and influence the images being created.
+.TP 8
+.B \-no-mouse
+Turns off \fB\-mouse\fP.
+.TP 8
+.B \-mouse-size integer
+In \fB\-mouse\fP mode, this sets the mass of the mouse (analogously to the
+\fB\-size\fP parameter.)
+.TP 8
+.B \-nowalls
+This will cause the balls to continue on past the edge of the
+screen or window. They will still be kept track of and can come back.
+.TP 8
+.B \-walls
+This will cause the balls to bounce when they get
+to the edge of the screen or window. This is the default behavior.
+.TP 8
+.B \-maxspeed
+Imposes a maximum speed (default). If a ball ends up going faster than
+this, it will be treated as though there were .9 viscosity until it is
+under the limit. This stops the balls from continually accelerating (which
+they have a tendency to do), but also causes balls moving very fast to
+tend to clump in the lower right corner.
+.TP 8
+.B \-nomaxspeed
+If this is specified, no maximum speed is set for the balls.
+.TP 8
+.B \-fast-bounce
+Uses the old, simple bouncing algorithm (default). This simply moves any
+ball that is out of bounds back to a wall and reverses its velocity.
+This works fine for most cases, but under some circumstances, the
+simplification can lead to annoying effects.
+.TP 8
+.B \-correct-bounce
+Uses a more intelligent bouncing algorithm. This method actually reflects
+the balls off the walls until they are within bounds. This can be slow
+if balls are bouncing a whole lot, perhaps because of -nomaxspeed.
+.TP 8
+.B \-graphmode none | x | y | both | speed
+For "x", "y", and "both", displays the given velocities of each ball as a
+bar graph in the same window as the balls. For "speed", displays the total
+speed of each ball. Default is "none".
+.BR
+.TP 8
+.B \-fps
+Display the current frame rate and CPU load.
+.SH ENVIRONMENT