diff --git a/geometry.scad b/geometry.scad
index 30e1d9d..7cda463 100644
--- a/geometry.scad
+++ b/geometry.scad
@@ -1689,9 +1689,10 @@ function furthest_point(pt, points) =
 //   area = polygon_area(poly);
 // Topics: Geometry, Polygons, Area
 // Description:
-//   Given a 2D or 3D planar polygon, returns the area of that polygon.
-//   If the polygon is self-crossing, the results are undefined. For non-planar 3D polygon the result is `undef`.
-//   When `signed` is true, a signed area is returned; a positive area indicates a clockwise polygon.
+//   Given a 2D or 3D simple planar polygon, returns the area of that polygon.
+//   If the polygon is self-intersecting or non-planar, the result is `undef.` 
+//   When `signed` is true and the polygon is 2d, a signed area is returned: a positive area indicates a counter-clockwise polygon.
+//   The area of 3d polygons is always nonnegative.  
 // Arguments:
 //   poly = Polygon to compute the area of.
 //   signed = If true, a signed area is returned. Default: false.
@@ -1706,7 +1707,7 @@ function polygon_area(poly, signed=false) =
         let(
             n = plane_normal(plane),  
             total = 
-                sum([ for(i=[1:1:len(poly)-2])
+                -sum([ for(i=[1:1:len(poly)-2])
                         cross(poly[i]-poly[0], poly[i+1]-poly[0]) 
                     ]) * n/2
         ) 
diff --git a/tests/test_geometry.scad b/tests/test_geometry.scad
index 19182c4..2c19e6d 100644
--- a/tests/test_geometry.scad
+++ b/tests/test_geometry.scad
@@ -32,7 +32,6 @@ test_tri_calc();
 //test_hyp_adj_to_ang();
 //test_hyp_opp_to_ang();
 //test_adj_opp_to_ang();
-test_triangle_area();
 test_plane3pt();
 test_plane3pt_indexed();
 test_plane_from_normal();
@@ -649,13 +648,6 @@ module test_hyp_opp_to_ang() nil();  // Covered in test_tri_functions()
 module test_adj_opp_to_ang() nil();  // Covered in test_tri_functions()
 
 
-module test_triangle_area() {
-    assert(abs(triangle_area([0,0], [0,10], [10,0]) + 50) < EPSILON);
-    assert(abs(triangle_area([0,0], [0,10], [0,15])) < EPSILON);
-    assert(abs(triangle_area([0,0], [10,0], [0,10]) - 50) < EPSILON);
-}
-*test_triangle_area();
-
 
 module test_plane3pt() {
     assert_approx(plane3pt([0,0,20], [0,10,10], [0,0,0]), [1,0,0,0]);
@@ -817,6 +809,10 @@ module test_polygon_area() {
     assert(approx(polygon_area(rot([13,27,75],
                                p=path3d(circle(r=50,$fn=1000),fill=23)),
                                signed=true), -PI*50*50, eps=0.1));
+    assert(abs(triangle_area([0,0], [0,10], [10,0]) + 50) < EPSILON);
+    assert(abs(triangle_area([0,0], [0,10], [0,15])) < EPSILON);
+    assert(abs(triangle_area([0,0], [10,0], [0,10]) - 50) < EPSILON);
+    
 }
 *test_polygon_area();