update doc

docs/lib-crystal_ball.md

@@ -9,6 +9,7 @@ Uses spherical coordinate system to create a crystal ball.
 - `radius` : The radial distance r. 
 - `theta` : The azimuthal angle. It defaults to 360. It also accepts a 2 element vector. The first element of the vector is the beginning angle in degrees, and the second element is the ending angle.
 - `phi` : The polar angle. It defaults to 180. It also accepts a 2 element vector. The first element of the vector is the beginning angle in degrees, and the second element is the ending angle.
+- `thickness` : The thickness of the ball. **Since:** 2.1.
 - `$fa`, `$fs`, `$fn` : Check [the circle module](https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Using_the_2D_Subsystem#circle) or [the sphere module](https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Primitive_Solids#sphere) for more details. The final fragments will be a multiple of 4 to fit edges.
 
 ## Examples
@@ -18,29 +19,31 @@ Uses spherical coordinate system to create a crystal ball.
 	include <polysections.scad>;
 	include <ring_extrude.scad>;
 	include <crystal_ball.scad>;
-	
+
 	crystal_ball(radius = 6);
-	
+
 	translate([12, 0, 0]) 
-	    crystal_ball(
-	        radius = 6, 
-	        theta = 270,
-	        $fn = 12
-	    );
-	
+		crystal_ball(
+			radius = 6, 
+			theta = 270,
+			thickness = 1,
+			$fn = 12
+		);
+
 	translate([24, 0, 0]) 
-	    crystal_ball(
-	        radius = 6, 
-	        theta = 270,
-	        phi = 90,
-	        $fn = 12
-	    );    
-	    
+		crystal_ball(
+			radius = 6, 
+			theta = 270,
+			phi = 90,
+			$fn = 12
+		);    
+
 	translate([36, 0, 0]) 
-	    crystal_ball(
-	        radius = 6, 
-	        theta = [-30, 270],
-	        phi = [30, 60]
-	    );        
+		crystal_ball(
+			radius = 6, 
+			theta = [-30, 270],
+			phi = [30, 60],
+			thickness = 2
+		);           
 
 ![crystal_ball](images/lib-crystal_ball-1.JPG)