diff --git a/src/body/Body.js b/src/body/Body.js
index 49fe717..b1973c9 100644
--- a/src/body/Body.js
+++ b/src/body/Body.js
@@ -399,7 +399,7 @@ var Axes = require('../geometry/Axes');
         }
 
         // sum the properties of all compound parts of the parent body
-        var total = _totalProperties(body);
+        var total = Body._totalProperties(body);
 
         body.area = total.area;
         body.parent = body;
@@ -658,7 +658,7 @@ var Axes = require('../geometry/Axes');
      * @param {body} body
      * @return {}
      */
-    var _totalProperties = function(body) {
+    Body._totalProperties = function(body) {
         // from equations at:
         // https://ecourses.ou.edu/cgi-bin/ebook.cgi?doc=&topic=st&chap_sec=07.2&page=theory
         // http://output.to/sideway/default.asp?qno=121100087
diff --git a/src/collision/Grid.js b/src/collision/Grid.js
index 317eea2..4acff1e 100644
--- a/src/collision/Grid.js
+++ b/src/collision/Grid.js
@@ -82,7 +82,7 @@ var Common = require('../core/Common');
                 || body.bounds.max.y < world.bounds.min.y || body.bounds.min.y > world.bounds.max.y)
                 continue;
 
-            var newRegion = _getRegion(grid, body);
+            var newRegion = Grid._getRegion(grid, body);
 
             // if the body has changed grid region
             if (!body.region || newRegion.id !== body.region.id || forceUpdate) {
@@ -94,13 +94,13 @@ var Common = require('../core/Common');
                 if (!body.region || forceUpdate)
                     body.region = newRegion;
 
-                var union = _regionUnion(newRegion, body.region);
+                var union = Grid._regionUnion(newRegion, body.region);
 
                 // update grid buckets affected by region change
                 // iterate over the union of both regions
                 for (col = union.startCol; col <= union.endCol; col++) {
                     for (row = union.startRow; row <= union.endRow; row++) {
-                        bucketId = _getBucketId(col, row);
+                        bucketId = Grid._getBucketId(col, row);
                         bucket = buckets[bucketId];
 
                         var isInsideNewRegion = (col >= newRegion.startCol && col <= newRegion.endCol
@@ -113,15 +113,15 @@ var Common = require('../core/Common');
                         if (!isInsideNewRegion && isInsideOldRegion) {
                             if (isInsideOldRegion) {
                                 if (bucket)
-                                    _bucketRemoveBody(grid, bucket, body);
+                                    Grid._bucketRemoveBody(grid, bucket, body);
                             }
                         }
 
                         // add to new region buckets
                         if (body.region === newRegion || (isInsideNewRegion && !isInsideOldRegion) || forceUpdate) {
                             if (!bucket)
-                                bucket = _createBucket(buckets, bucketId);
-                            _bucketAddBody(grid, bucket, body);
+                                bucket = Grid._createBucket(buckets, bucketId);
+                            Grid._bucketAddBody(grid, bucket, body);
                         }
                     }
                 }
@@ -136,7 +136,7 @@ var Common = require('../core/Common');
 
         // update pairs list only if pairs changed (i.e. a body changed region)
         if (gridChanged)
-            grid.pairsList = _createActivePairsList(grid);
+            grid.pairsList = Grid._createActivePairsList(grid);
     };
 
     /**
@@ -158,13 +158,13 @@ var Common = require('../core/Common');
      * @param {} regionB
      * @return {} region
      */
-    var _regionUnion = function(regionA, regionB) {
+    Grid._regionUnion = function(regionA, regionB) {
         var startCol = Math.min(regionA.startCol, regionB.startCol),
             endCol = Math.max(regionA.endCol, regionB.endCol),
             startRow = Math.min(regionA.startRow, regionB.startRow),
             endRow = Math.max(regionA.endRow, regionB.endRow);
 
-        return _createRegion(startCol, endCol, startRow, endRow);
+        return Grid._createRegion(startCol, endCol, startRow, endRow);
     };
 
     /**
@@ -175,14 +175,14 @@ var Common = require('../core/Common');
      * @param {} body
      * @return {} region
      */
-    var _getRegion = function(grid, body) {
+    Grid._getRegion = function(grid, body) {
         var bounds = body.bounds,
             startCol = Math.floor(bounds.min.x / grid.bucketWidth),
             endCol = Math.floor(bounds.max.x / grid.bucketWidth),
             startRow = Math.floor(bounds.min.y / grid.bucketHeight),
             endRow = Math.floor(bounds.max.y / grid.bucketHeight);
 
-        return _createRegion(startCol, endCol, startRow, endRow);
+        return Grid._createRegion(startCol, endCol, startRow, endRow);
     };
 
     /**
@@ -195,7 +195,7 @@ var Common = require('../core/Common');
      * @param {} endRow
      * @return {} region
      */
-    var _createRegion = function(startCol, endCol, startRow, endRow) {
+    Grid._createRegion = function(startCol, endCol, startRow, endRow) {
         return { 
             id: startCol + ',' + endCol + ',' + startRow + ',' + endRow,
             startCol: startCol, 
@@ -213,7 +213,7 @@ var Common = require('../core/Common');
      * @param {} row
      * @return {string} bucket id
      */
-    var _getBucketId = function(column, row) {
+    Grid._getBucketId = function(column, row) {
         return 'C' + column + 'R' + row;
     };
 
@@ -225,7 +225,7 @@ var Common = require('../core/Common');
      * @param {} bucketId
      * @return {} bucket
      */
-    var _createBucket = function(buckets, bucketId) {
+    Grid._createBucket = function(buckets, bucketId) {
         var bucket = buckets[bucketId] = [];
         return bucket;
     };
@@ -238,7 +238,7 @@ var Common = require('../core/Common');
      * @param {} bucket
      * @param {} body
      */
-    var _bucketAddBody = function(grid, bucket, body) {
+    Grid._bucketAddBody = function(grid, bucket, body) {
         // add new pairs
         for (var i = 0; i < bucket.length; i++) {
             var bodyB = bucket[i];
@@ -270,7 +270,7 @@ var Common = require('../core/Common');
      * @param {} bucket
      * @param {} body
      */
-    var _bucketRemoveBody = function(grid, bucket, body) {
+    Grid._bucketRemoveBody = function(grid, bucket, body) {
         // remove from bucket
         bucket.splice(Common.indexOf(bucket, body), 1);
 
@@ -294,7 +294,7 @@ var Common = require('../core/Common');
      * @param {} grid
      * @return [] pairs
      */
-    var _createActivePairsList = function(grid) {
+    Grid._createActivePairsList = function(grid) {
         var pairKeys,
             pair,
             pairs = [];
diff --git a/src/collision/Pairs.js b/src/collision/Pairs.js
index 48bd2ac..996952d 100644
--- a/src/collision/Pairs.js
+++ b/src/collision/Pairs.js
@@ -13,7 +13,7 @@ var Common = require('../core/Common');
 
 (function() {
     
-    var _pairMaxIdleLife = 1000;
+    Pairs._pairMaxIdleLife = 1000;
 
     /**
      * Creates a new pairs structure.
@@ -124,7 +124,7 @@ var Common = require('../core/Common');
             }
 
             // if pair is inactive for too long, mark it to be removed
-            if (timestamp - pair.timeUpdated > _pairMaxIdleLife) {
+            if (timestamp - pair.timeUpdated > Pairs._pairMaxIdleLife) {
                 indexesToRemove.push(i);
             }
         }
diff --git a/src/collision/SAT.js b/src/collision/SAT.js
index 5c3d669..29a58c3 100644
--- a/src/collision/SAT.js
+++ b/src/collision/SAT.js
@@ -54,7 +54,7 @@ var Vector = require('../geometry/Vector');
                 axisBodyB = axisBodyA === bodyA ? bodyB : bodyA,
                 axes = [axisBodyA.axes[previousCollision.axisNumber]];
 
-            minOverlap = _overlapAxes(axisBodyA.vertices, axisBodyB.vertices, axes);
+            minOverlap = SAT._overlapAxes(axisBodyA.vertices, axisBodyB.vertices, axes);
             collision.reused = true;
 
             if (minOverlap.overlap <= 0) {
@@ -64,14 +64,14 @@ var Vector = require('../geometry/Vector');
         } else {
             // if we can't reuse a result, perform a full SAT test
 
-            overlapAB = _overlapAxes(bodyA.vertices, bodyB.vertices, bodyA.axes);
+            overlapAB = SAT._overlapAxes(bodyA.vertices, bodyB.vertices, bodyA.axes);
 
             if (overlapAB.overlap <= 0) {
                 collision.collided = false;
                 return collision;
             }
 
-            overlapBA = _overlapAxes(bodyB.vertices, bodyA.vertices, bodyB.axes);
+            overlapBA = SAT._overlapAxes(bodyB.vertices, bodyA.vertices, bodyB.axes);
 
             if (overlapBA.overlap <= 0) {
                 collision.collided = false;
@@ -120,7 +120,7 @@ var Vector = require('../geometry/Vector');
         collision.penetration.y = collision.normal.y * collision.depth; 
 
         // find support points, there is always either exactly one or two
-        var verticesB = _findSupports(bodyA, bodyB, collision.normal),
+        var verticesB = SAT._findSupports(bodyA, bodyB, collision.normal),
             supports = [];
 
         // find the supports from bodyB that are inside bodyA
@@ -132,7 +132,7 @@ var Vector = require('../geometry/Vector');
 
         // find the supports from bodyA that are inside bodyB
         if (supports.length < 2) {
-            var verticesA = _findSupports(bodyB, bodyA, Vector.neg(collision.normal));
+            var verticesA = SAT._findSupports(bodyB, bodyA, Vector.neg(collision.normal));
                 
             if (Vertices.contains(bodyB.vertices, verticesA[0]))
                 supports.push(verticesA[0]);
@@ -159,7 +159,7 @@ var Vector = require('../geometry/Vector');
      * @param {} axes
      * @return result
      */
-    var _overlapAxes = function(verticesA, verticesB, axes) {
+    SAT._overlapAxes = function(verticesA, verticesB, axes) {
         var projectionA = Vector._temp[0], 
             projectionB = Vector._temp[1],
             result = { overlap: Number.MAX_VALUE },
@@ -169,8 +169,8 @@ var Vector = require('../geometry/Vector');
         for (var i = 0; i < axes.length; i++) {
             axis = axes[i];
 
-            _projectToAxis(projectionA, verticesA, axis);
-            _projectToAxis(projectionB, verticesB, axis);
+            SAT._projectToAxis(projectionA, verticesA, axis);
+            SAT._projectToAxis(projectionB, verticesB, axis);
 
             overlap = Math.min(projectionA.max - projectionB.min, projectionB.max - projectionA.min);
 
@@ -197,7 +197,7 @@ var Vector = require('../geometry/Vector');
      * @param {} vertices
      * @param {} axis
      */
-    var _projectToAxis = function(projection, vertices, axis) {
+    SAT._projectToAxis = function(projection, vertices, axis) {
         var min = Vector.dot(vertices[0], axis),
             max = min;
 
@@ -224,7 +224,7 @@ var Vector = require('../geometry/Vector');
      * @param {} normal
      * @return [vector]
      */
-    var _findSupports = function(bodyA, bodyB, normal) {
+    SAT._findSupports = function(bodyA, bodyB, normal) {
         var nearestDistance = Number.MAX_VALUE,
             vertexToBody = Vector._temp[0],
             vertices = bodyB.vertices,
diff --git a/src/constraint/MouseConstraint.js b/src/constraint/MouseConstraint.js
index fa1734a..4dc5561 100644
--- a/src/constraint/MouseConstraint.js
+++ b/src/constraint/MouseConstraint.js
@@ -77,7 +77,7 @@ var Bounds = require('../geometry/Bounds');
         Events.on(engine, 'beforeUpdate', function() {
             var allBodies = Composite.allBodies(engine.world);
             MouseConstraint.update(mouseConstraint, allBodies);
-            _triggerEvents(mouseConstraint);
+            MouseConstraint._triggerEvents(mouseConstraint);
         });
 
         return mouseConstraint;
@@ -136,7 +136,7 @@ var Bounds = require('../geometry/Bounds');
      * @private
      * @param {mouse} mouseConstraint
      */
-    var _triggerEvents = function(mouseConstraint) {
+    MouseConstraint._triggerEvents = function(mouseConstraint) {
         var mouse = mouseConstraint.mouse,
             mouseEvents = mouse.sourceEvents;
 
diff --git a/src/core/Common.js b/src/core/Common.js
index f020b9c..143204f 100644
--- a/src/core/Common.js
+++ b/src/core/Common.js
@@ -424,14 +424,14 @@ module.exports = Common;
 
         for (var node in graph) {
             if (!visited[node] && !temp[node]) {
-                _topologicalSort(node, visited, temp, graph, result);
+                Common._topologicalSort(node, visited, temp, graph, result);
             }
         }
 
         return result;
     };
 
-    var _topologicalSort = function(node, visited, temp, graph, result) {
+    Common._topologicalSort = function(node, visited, temp, graph, result) {
         var neighbors = graph[node] || [];
         temp[node] = true;
 
@@ -444,7 +444,7 @@ module.exports = Common;
             }
 
             if (!visited[neighbor]) {
-                _topologicalSort(neighbor, visited, temp, graph, result);
+                Common._topologicalSort(neighbor, visited, temp, graph, result);
             }
         }
 
diff --git a/src/core/Mouse.js b/src/core/Mouse.js
index 53e2695..9bc7dd9 100644
--- a/src/core/Mouse.js
+++ b/src/core/Mouse.js
@@ -44,7 +44,7 @@ var Common = require('../core/Common');
         };
         
         mouse.mousemove = function(event) { 
-            var position = _getRelativeMousePosition(event, mouse.element, mouse.pixelRatio),
+            var position = Mouse._getRelativeMousePosition(event, mouse.element, mouse.pixelRatio),
                 touches = event.changedTouches;
 
             if (touches) {
@@ -60,7 +60,7 @@ var Common = require('../core/Common');
         };
         
         mouse.mousedown = function(event) {
-            var position = _getRelativeMousePosition(event, mouse.element, mouse.pixelRatio),
+            var position = Mouse._getRelativeMousePosition(event, mouse.element, mouse.pixelRatio),
                 touches = event.changedTouches;
 
             if (touches) {
@@ -80,7 +80,7 @@ var Common = require('../core/Common');
         };
         
         mouse.mouseup = function(event) {
-            var position = _getRelativeMousePosition(event, mouse.element, mouse.pixelRatio),
+            var position = Mouse._getRelativeMousePosition(event, mouse.element, mouse.pixelRatio),
                 touches = event.changedTouches;
 
             if (touches) {
@@ -176,7 +176,7 @@ var Common = require('../core/Common');
      * @param {number} pixelRatio
      * @return {}
      */
-    var _getRelativeMousePosition = function(event, element, pixelRatio) {
+    Mouse._getRelativeMousePosition = function(event, element, pixelRatio) {
         var elementBounds = element.getBoundingClientRect(),
             rootNode = (document.documentElement || document.body.parentNode || document.body),
             scrollX = (window.pageXOffset !== undefined) ? window.pageXOffset : rootNode.scrollLeft,
diff --git a/src/geometry/Svg.js b/src/geometry/Svg.js
index 971d0ab..9c0f65d 100644
--- a/src/geometry/Svg.js
+++ b/src/geometry/Svg.js
@@ -97,7 +97,7 @@ var Bounds = require('../geometry/Bounds');
         };
 
         // ensure path is absolute
-        _svgPathToAbsolute(path);
+        Svg._svgPathToAbsolute(path);
 
         // get total length
         total = path.getTotalLength();
@@ -149,7 +149,7 @@ var Bounds = require('../geometry/Bounds');
         return points;
     };
 
-    var _svgPathToAbsolute = function(path) {
+    Svg._svgPathToAbsolute = function(path) {
         // http://phrogz.net/convert-svg-path-to-all-absolute-commands
         // Copyright (c) Gavin Kistner
         // http://phrogz.net/js/_ReuseLicense.txt