diff --git a/Gruntfile.js b/Gruntfile.js
index 58006c80..42d62b78 100644
--- a/Gruntfile.js
+++ b/Gruntfile.js
@@ -140,6 +140,7 @@ module.exports = function (grunt) {
         'src/physics/Spring.js',
         'src/physics/Material.js',
         'src/physics/ContactMaterial.js',
+        'src/physics/CollisionGroup.js',
 
         'src/particles/Particles.js',
         'src/particles/arcade/ArcadeParticles.js',
diff --git a/build/config.php b/build/config.php
index 3940453f..fb00fa88 100644
--- a/build/config.php
+++ b/build/config.php
@@ -186,6 +186,7 @@
     <script src="$path/src/physics/Spring.js"></script>
     <script src="$path/src/physics/Material.js"></script>
     <script src="$path/src/physics/ContactMaterial.js"></script>
+    <script src="$path/src/physics/CollisionGroup.js"></script>
 
     <script src="$path/src/particles/Particles.js"></script>
     <script src="$path/src/particles/arcade/ArcadeParticles.js"></script>
diff --git a/examples/wip/cannon.js b/examples/wip/cannon.js
index ce9069de..0ed68d25 100644
--- a/examples/wip/cannon.js
+++ b/examples/wip/cannon.js
@@ -6,6 +6,7 @@ function preload() {
     // game.load.image('arrow', 'assets/sprites/arrow.png');
     game.load.image('arrow', 'assets/sprites/thrust_ship2.png');
     game.load.image('chunk', 'assets/sprites/chunk.png');
+    game.load.image('box', 'assets/sprites/block.png');
     game.load.spritesheet('bullets', 'assets/sprites/balls.png', 17, 17);
 
 }
@@ -16,6 +17,13 @@ var angle = 0;
 var fireRate = 100;
 var nextFire = 0;
 var cursors;
+// var PLAYER;
+// var BULLET;
+// var WORLD;
+var boxes;
+var playerGroup;
+var bulletGroup;
+var boxGroup;
 
 function create() {
 
@@ -29,9 +37,38 @@ function create() {
     bullets.createMultiple(250, 'bullets', 0, false);
 
     cannon = game.add.sprite(50, 500, 'arrow');
+    cannon.name = 'ship';
     cannon.physicsEnabled = true;
-    cannon.body.kinematic = true;
-    cannon.body.mass = 4;
+
+    playerGroup = game.physics.createCollisionGroup();
+    bulletGroup = game.physics.createCollisionGroup();
+    boxGroup = game.physics.createCollisionGroup();
+
+    // cannon.body.data.shapes[0].collisionGroup = PLAYER.mask;
+    // cannon.body.data.shapes[0].collisionMask = game.physics.WORLD.mask;
+
+    cannon.body.setCollisionGroup(playerGroup);
+    cannon.body.collides(boxGroup);
+
+
+    boxes = game.add.group();
+
+    for (var i = 0; i < 10; i++)
+    {
+        var box = boxes.create(game.rnd.integerInRange(100, 700), game.rnd.integerInRange(100, 500), 'box');
+        box.name = 'box' + i;
+        box.scale.set(0.5);
+        // box.scale.set(game.rnd.realInRange(0.2, 0.7));
+        box.physicsEnabled = true;
+        box.body.setCollisionGroup(boxGroup);
+        box.body.collides(playerGroup);
+        box.body.collides(bulletGroup);
+        // box.body.mass = 10;
+        // box.body.setMaterial(boxMaterial);
+        // box.body.fixedRotation = true;
+    }
+
+
     cursors = game.input.keyboard.createCursorKeys();
 
 }
@@ -58,6 +95,12 @@ function fire() {
 
             bullet.body.velocity.x = magnitude * Math.cos(angle);
             bullet.body.velocity.y = magnitude * Math.sin(angle);
+
+            bullet.body.setCollisionGroup(bulletGroup);
+            bullet.body.collides(boxGroup);
+
+            // bullet.body.data.shapes[0].collisionGroup = BULLET;
+            // bullet.body.data.shapes[0].collisionMask = WORLD | BULLET;
         }
     }
 
@@ -80,11 +123,13 @@ function update() {
 
     if (cursors.up.isDown)
     {
-        cannon.body.moveForward(200);
+        // cannon.body.moveForward(200);
+        cannon.body.thrust(200);
     }
     else if (cursors.down.isDown)
     {
-        cannon.body.moveBackward(200);
+        // cannon.body.moveBackward(200);
+        cannon.body.reverse(200);
     }
 
     var dx = game.input.activePointer.worldX - cannon.x;
diff --git a/examples/wip/platforms.js b/examples/wip/platforms.js
index 528e2ce6..b4e792d3 100644
--- a/examples/wip/platforms.js
+++ b/examples/wip/platforms.js
@@ -14,8 +14,8 @@ var facing = 'left';
 var jumpTimer = 0;
 var cursors;
 var jumpButton;
-var box1;
-var box2;
+
+var boxes;
 
 function create() {
 
@@ -39,40 +39,53 @@ function create() {
 
     // game.physics.setBoundsToWorld();
 
-    game.physics.gravity.y = 20;
+    // game.physics.gravity.y = 9.78;
+    game.physics.setBoundsToWorld(true, true, false, true);
+
+    game.physics.world.gravity[1] = -20;
     game.physics.friction = 0.5;
+    game.physics.world.solver.stiffness = 1e20;
+    game.physics.world.solver.relaxation = 3;
 
     //  Materials
     var groundMaterial = game.physics.createMaterial('ground');
     var characterMaterial = game.physics.createMaterial('character');
     var boxMaterial = game.physics.createMaterial('box');
 
-    player = game.add.sprite(32, 320, 'dude');
+    player = game.add.sprite(100, -400, 'dude');
     player.physicsEnabled = true;
     player.body.fixedRotation = true;
     player.body.setMaterial(characterMaterial);
+    player.body.mass = 1;
+    player.body.damping = 0.5;
 
     player.animations.add('left', [0, 1, 2, 3], 10, true);
     player.animations.add('turn', [4], 20, true);
     player.animations.add('right', [5, 6, 7, 8], 10, true);
 
-    box1 = game.add.sprite(200, 300, 'box');
-    box1.physicsEnabled = true;
-    // box1.body.fixedRotation = true;
-    box1.body.setMaterial(boxMaterial);
+    boxes = game.add.group();
 
-    box2 = game.add.sprite(400, 300, 'box');
-    box2.physicsEnabled = true;
-    // box2.body.fixedRotation = true;
-    box2.body.setMaterial(boxMaterial);
+    for (var i = 0; i < 50; i++)
+    {
+        var box = boxes.create(game.rnd.integerInRange(200, 700), game.rnd.integerInRange(-200, 400), 'box');
+        // box.scale.set(0.5);
+        box.scale.set(game.rnd.realInRange(0.2, 0.7));
+        box.physicsEnabled = true;
+        box.body.mass = 10;
+        box.body.setMaterial(boxMaterial);
+        box.body.fixedRotation = true;
+    }
 
     //  Set the material along the ground
-    game.physics.setWorldMaterial(groundMaterial, false, false, false, true);
+    game.physics.setWorldMaterial(groundMaterial);
 
     var groundCharacterCM = game.physics.createContactMaterial(groundMaterial, characterMaterial, { friction: 0.0 }); // no friction between character and ground
     var boxCharacterCM = game.physics.createContactMaterial(boxMaterial, characterMaterial, { friction: 0.0 }); // No friction between character and boxes
     var boxGroundCM = game.physics.createContactMaterial(boxMaterial, groundMaterial, { friction: 0.6 }); // Between boxes and ground
 
+    console.log(groundCharacterCM);
+    console.log(boxGroundCM);
+
     // game.camera.follow(player);
 
     cursors = game.input.keyboard.createCursorKeys();
@@ -82,11 +95,9 @@ function create() {
 
 function update() {
 
-    player.body.velocity.x = 0;
-
     if (cursors.left.isDown)
     {
-        player.body.moveLeft(150);
+        player.body.moveLeft(200);
 
         if (facing != 'left')
         {
@@ -96,7 +107,7 @@ function update() {
     }
     else if (cursors.right.isDown)
     {
-        player.body.moveRight(150);
+        player.body.moveRight(200);
 
         if (facing != 'right')
         {
@@ -106,6 +117,8 @@ function update() {
     }
     else
     {
+        player.body.velocity.x = 0;
+
         if (facing != 'idle')
         {
             player.animations.stop();
@@ -150,7 +163,7 @@ function render () {
 
     // if (player.debug)
     // {
-    //     game.debug.renderPhysicsBody(player.body);
+        game.debug.renderPhysicsBody(player.body);
     //     game.debug.renderBodyInfo(player, 16, 24);
     // }
 
diff --git a/src/math/Math.js b/src/math/Math.js
index fd1dfd89..a1876cb6 100644
--- a/src/math/Math.js
+++ b/src/math/Math.js
@@ -1292,7 +1292,7 @@ Phaser.Math = {
     },
 
     /**
-    * Convert p2 physics value to pixel scale.
+    * Convert p2 physics value (meters) to pixel scale.
     * 
     * @method Phaser.Math#p2px
     * @param {number} v - The value to convert.
@@ -1303,7 +1303,7 @@ Phaser.Math = {
     },
 
     /**
-    * Convert pixel value to p2 physics scale.
+    * Convert pixel value to p2 physics scale (meters).
     * 
     * @method Phaser.Math#px2p
     * @param {number} v - The value to convert.
diff --git a/src/physics/Body.js b/src/physics/Body.js
index 8fc62f6c..9e1faf87 100644
--- a/src/physics/Body.js
+++ b/src/physics/Body.js
@@ -63,6 +63,19 @@ Phaser.Physics.Body = function (game, sprite, x, y, mass) {
     */
     this.gravity = new Phaser.Point();
 
+    /**
+    * A Body can be set to collide against the World bounds automatically if this is set to true. Otherwise it will leave the World.
+    * Note that this only applies if your World has bounds! The response to the collision should be managed via CollisionMaterials.
+    * @property {boolean} collideWorldBounds - Should the Body collide with the World bounds?
+    */
+    this.collideWorldBounds = true;
+
+    /**
+    * @property {array} collidesWith - Array of CollisionGroups that this Bodies shapes collide with.
+    * @private
+    */
+    this.collidesWith = [];
+
     // this.onAdded = new Phaser.Signal();
     // this.onRemoved = new Phaser.Signal();
 
@@ -77,6 +90,66 @@ Phaser.Physics.Body = function (game, sprite, x, y, mass) {
 
 Phaser.Physics.Body.prototype = {
 
+    setCollisionGroup: function (group, shape) {
+
+        if (typeof shape === 'undefined')
+        {
+            for (var i = this.data.shapes.length - 1; i >= 0; i--)
+            {
+                this.data.shapes[i].collisionGroup = group.mask;
+            }
+        }
+        else
+        {
+            shape.collisionGroup = group.mask;
+        }
+
+    },
+
+    /**
+    * Adds the given CollisionGroup to the list of groups that this body will collide with and updates the collision mask.
+    *
+    * @method Phaser.Physics.Body#collides
+    * @param {Phaser.Physics.CollisionGroup} group - The Collision Group that this Bodies shapes will collide with.
+    * @param {p2.Shape} [shape] - An optional Shape. If not provided the collision mask will be added to all Shapes in this Body.
+    */
+    collides: function (group, shape) {
+
+        //  TODO: group can be an array
+
+        if (this.collidesWith.indexOf(group) === -1)
+        {
+            this.collidesWith.push(group);
+        }
+
+        var mask = 0;
+
+        if (this.collideWorldBounds)
+        {
+            mask = this.game.physics.boundsCollisionGroup.mask;
+        }
+
+        for (var i = 0; i < this.collidesWith.length; i++)
+        {
+            mask = mask | this.collidesWith[i].mask;
+        }
+
+        if (typeof shape === 'undefined')
+        {
+            for (var i = this.data.shapes.length - 1; i >= 0; i--)
+            {
+                this.data.shapes[i].collisionMask = mask;
+            }
+        }
+        else
+        {
+            shape.collisionMask = mask;
+        }
+
+        console.log('collides', this.sprite.name, group, mask);
+
+    },
+
     /**
     * Moves the shape offsets so their center of mass becomes the body center of mass.
     *
@@ -819,7 +892,7 @@ Phaser.Physics.Body.prototype = {
     },
 
     /**
-    * Convert p2 physics value to pixel scale.
+    * Convert p2 physics value (meters) to pixel scale.
     * 
     * @method Phaser.Math#p2px
     * @param {number} v - The value to convert.
@@ -832,7 +905,7 @@ Phaser.Physics.Body.prototype = {
     },
 
     /**
-    * Convert pixel value to p2 physics scale.
+    * Convert pixel value to p2 physics scale (meters).
     * 
     * @method Phaser.Math#px2p
     * @param {number} v - The value to convert.
diff --git a/src/physics/CollisionGroup.js b/src/physics/CollisionGroup.js
new file mode 100644
index 00000000..5f27ea57
--- /dev/null
+++ b/src/physics/CollisionGroup.js
@@ -0,0 +1,21 @@
+/**
+* @author       Richard Davey <rich@photonstorm.com>
+* @copyright    2014 Photon Storm Ltd.
+* @license      {@link https://github.com/photonstorm/phaser/blob/master/license.txt|MIT License}
+*/
+
+/**
+* Collision Group
+*
+* @class Phaser.Physics.CollisionGroup
+* @classdesc Physics Collision Group Constructor
+* @constructor
+*/
+Phaser.Physics.CollisionGroup = function (bitmask) {
+
+    /**
+    * @property {number} mask - The CollisionGroup bitmask.
+    */
+    this.mask = bitmask;
+
+}
diff --git a/src/physics/World.js b/src/physics/World.js
index 18dfdd9b..bd712490 100644
--- a/src/physics/World.js
+++ b/src/physics/World.js
@@ -132,6 +132,20 @@ Phaser.Physics.World = function (game) {
     this.world.on("beginContact", this.beginContactHandler, this);
     this.world.on("endContact", this.endContactHandler, this);
 
+    /**
+    * @property {array} collisionGroups - Internal var.
+    */
+    this.collisionGroups = [];
+
+    /**
+    * @property {number} _collisionGroupID - Internal var.
+    * @private
+    */
+    this._collisionGroupID = 2;
+
+    this.boundsCollisionGroup = new Phaser.Physics.CollisionGroup(2);
+    this.boundsCollidesWith = [];
+
     this.setBoundsToWorld(true, true, true, true);
 
 };
@@ -310,24 +324,28 @@ Phaser.Physics.World.prototype = {
         if (left)
         {
             this._wallShapes[0] = new p2.Plane();
+            this._wallShapes[0].collisionGroup = this.boundsCollisionGroup.mask;
             this.bounds.addShape(this._wallShapes[0], [this.game.math.px2p(-hw), 0], 1.5707963267948966 );
         }
 
         if (right)
         {
             this._wallShapes[1] = new p2.Plane();
+            this._wallShapes[1].collisionGroup = this.boundsCollisionGroup.mask;
             this.bounds.addShape(this._wallShapes[1], [this.game.math.px2p(hw), 0], -1.5707963267948966 );
         }
 
         if (top)
         {
             this._wallShapes[2] = new p2.Plane();
+            this._wallShapes[2].collisionGroup = this.boundsCollisionGroup.mask;
             this.bounds.addShape(this._wallShapes[2], [0, this.game.math.px2p(-hh)], -3.141592653589793 );
         }
 
         if (bottom)
         {
             this._wallShapes[3] = new p2.Plane();
+            this._wallShapes[3].collisionGroup = this.boundsCollisionGroup.mask;
             this.bounds.addShape(this._wallShapes[3], [0, this.game.math.px2p(hh)] );
         }
 
@@ -662,6 +680,43 @@ Phaser.Physics.World.prototype = {
 
     },
 
+    createCollisionGroup: function () {
+
+        var bitmask = Math.pow(2, this._collisionGroupID);
+
+        //  Add it to the bounds mask automatically (they won't collide with it unless it's added back by the other group)
+        // this.boundsCollisionGroup.mask = this.boundsCollisionGroup.mask | bitmask;
+
+        if (this._wallShapes[0])
+        {
+            this._wallShapes[0].collisionMask = this._wallShapes[0].collisionMask | bitmask;
+        }
+
+        if (this._wallShapes[1])
+        {
+            this._wallShapes[1].collisionMask = this._wallShapes[1].collisionMask | bitmask;
+        }
+
+        if (this._wallShapes[2])
+        {
+            this._wallShapes[2].collisionMask = this._wallShapes[2].collisionMask | bitmask;
+        }
+
+        if (this._wallShapes[3])
+        {
+            this._wallShapes[3].collisionMask = this._wallShapes[3].collisionMask | bitmask;
+        }
+
+        this._collisionGroupID++;
+
+        var group = new Phaser.Physics.CollisionGroup(bitmask);
+
+        this.collisionGroups.push(group);
+
+        return group;
+
+    },
+
     /**
     * @method Phaser.Physics.World.prototype.createBody
     * @param {number} x - The x coordinate of Body.