Updated World vastly. No longer extends p2.World due to a few vars we can't alias cleanly, adds in lots of new helper methods.

Ready for Materials and Constraints.
InversePointProxy is for aliasing a p2 typed array when the values need reversing before applying (gravity for example).

src/physics/InversePointProxy.js

@@ -0,0 +1,61 @@
+/**
+* @author       Richard Davey <rich@photonstorm.com>
+* @copyright    2014 Photon Storm Ltd.
+* @license      {@link https://github.com/photonstorm/phaser/blob/master/license.txt|MIT License}
+*/
+
+/**
+* A InversePointProxy is an internal class that allows for direct getter/setter style property access to Arrays and TypedArrays but inverses the values on set.
+*
+* @class Phaser.Physics.InversePointProxy
+* @classdesc InversePointProxy
+* @constructor
+* @param {any} destination - The object to bind to.
+*/
+Phaser.Physics.InversePointProxy = function (destination) {
+
+	this.destination = destination;
+
+};
+
+Phaser.Physics.InversePointProxy.prototype.constructor = Phaser.Physics.InversePointProxy;
+
+/**
+* @name Phaser.Physics.InversePointProxy#x
+* @property {number} x - The x property of this InversePointProxy.
+*/
+Object.defineProperty(Phaser.Physics.InversePointProxy.prototype, "x", {
+    
+    get: function () {
+
+        return this.destination[0];
+
+    },
+
+    set: function (value) {
+
+        this.destination[0] *= -value;
+
+    }
+
+});
+
+/**
+* @name Phaser.Physics.InversePointProxy#y
+* @property {number} y - The y property of this InversePointProxy.
+*/
+Object.defineProperty(Phaser.Physics.InversePointProxy.prototype, "y", {
+    
+    get: function () {
+
+        return this.destination[1];
+
+    },
+
+    set: function (value) {
+
+        this.destination[1] *= -value;
+
+    }
+
+});