Fix flipped right/left normal vector functions

geom/math.py

@@ -20,12 +20,12 @@ def normalize(x, y):
 
 def lnormal(x, y):
     """Returns the left-hand normal of a vector."""
-    return -y, x
+    return y, -x
 
 
 def rnormal(x, y):
     """Returns the right-hand normal of a vector."""
-    return y, -x
+    return -y, x
 
 
 def reverse(x, y):