Spivak

I hope that almost all of this is self-explanatory.
The 'S' in Spivak is supposed to stand for 'simple'.
0.  Downloading
The program is distributed in a disk image (.dmg) file.
Save the .dmg to disk; double click to open it, then drag
the application to your desktop, or Applications folder.
1. Entering formulas
The three wide fields at the top, center of the window are
the components of the parametrization.

The formula parser knows the following functions:
	sin		cos		tan
	sinh		cosh		tanh
	arcsin		arccos		arctan
	arcsinh		arccosh		arctanh
	exp		ln
and the following binary operations, with their usual precedence:
	+	-	*	/	^
You can refer to the constants
	pi	and 	e
by name in your formulas.  Use 'u' and 'v' for your parameters; other 
variable names will be treated as if they are zero.

2.  Choosing a point (and direction)
Click and drag in the upper left ('domain') window to choose a point
in the (u,v) plane, and you'll see the corresponding point marked on
the surface in the main window.

To choose a direction (for a geodesic, or tangent line), Control-click
in the domain window.  You'll mark a green reference point, and the implied
direction vector is from the white point toward the green point.

You can also use the vertical slider at the far right of the screen
to change the direction vector.
3.  Adjusting the view
You can click and drag in the main window to rotate the view, and you
can Control-click-and-drag to zoom in and out.  The small slider on 
the right controls the size of any decorations you're currently drawing.

4.  Writing the rest of the documentation
This is currently happening.