Allow tweaking z buffer when rendering polygon, improve explosion render

src/Geometry/Vector.hs

@@ -115,12 +115,10 @@ Identical to detV.  -}
 crossV :: Point2 -> Point2 -> Float
 crossV (ax,ay) (bx,by) = ax*by - ay*bx
 {- | TO CHECK Orthographic projection of one vector onto another. -}
-projV 
-    :: Point2
-    -> Point2
-    -> Point2
+projV :: Point2 -> Point2 -> Point2
 projV fromv onv 
     | den == 0  = error "tried projecting onto zero vector"
     | otherwise = (fromv `dotV` onv) / den *.* onv
   where
     den = onv `dotV` onv
+