diff --git a/Code/GamePhysics/Implementation/PhysicsAPI_Impl.cpp b/Code/GamePhysics/Implementation/PhysicsAPI_Impl.cpp
index b3abf32c..ae190608 100644
--- a/Code/GamePhysics/Implementation/PhysicsAPI_Impl.cpp
+++ b/Code/GamePhysics/Implementation/PhysicsAPI_Impl.cpp
@@ -3,6 +3,7 @@
 #include "SimpleRigidBody.h"
 #include "SphericalRigidBody.h"
 
+using namespace ::Oyster;
 using namespace ::Oyster::Physics;
 using namespace ::Oyster::Math;
 using namespace ::Oyster::Collision3D;
@@ -113,6 +114,7 @@ API_Impl::API_Impl()
 	this->gravityConstant = Constant::gravity_constant;
 	this->updateFrameLength = 1.0f / 120.0f;
 	this->destructionAction = Default::EventAction_Destruction;
+	this->gravity = ::std::vector<Gravity>();
 	this->worldScene = Octree();
 }
 
@@ -121,6 +123,8 @@ API_Impl::~API_Impl() {}
 void API_Impl::Init( unsigned int numObjects, unsigned int numGravityWells , const Float3 &worldSize )
 {
 	unsigned char numLayers = 4; //!< @todo TODO: calc numLayers from worldSize
+	this->gravity.resize( 0 );
+	this->gravity.reserve( numGravityWells );
 	this->worldScene = Octree( numObjects, numLayers, worldSize );
 }
 
@@ -153,14 +157,39 @@ float API_Impl::GetFrameTimeLength() const
 
 void API_Impl::Update()
 { /** @todo TODO: Update is a temporary solution .*/
-	
-
-
 	::std::vector<ICustomBody*> updateList;
+	ICustomBody::State state;
 	auto proto = this->worldScene.Sample( Universe(), updateList ).begin();
 	for( ; proto != updateList.end(); ++proto )
 	{
-		// Step 1: @todo TODO: Apply Gravity
+		// Step 1: Apply Gravity
+		(*proto)->GetState( state );
+		for( ::std::vector<Gravity>::size_type i = 0; i < this->gravity.size(); ++i )
+		{
+			switch( this->gravity[i].gravityType )
+			{
+			case Gravity::GravityType_Well:
+				{
+					Float4 d = state.GetCenterPosition() - Float4( this->gravity[i].well.position, 1.0f );
+					Float rSquared = d.Dot( d );
+					if( rSquared != 0.0 )
+					{
+						Float force = Physics3D::Formula::ForceField( this->gravityConstant, state.GetMass(), this->gravity[i].well.mass, rSquared );
+						state.ApplyLinearImpulse( (this->updateFrameLength * force / ::std::sqrt(rSquared)) * d );
+					}
+					break;
+				}
+			case Gravity::GravityType_Directed:
+				state.ApplyLinearImpulse( Float4(this->gravity[i].directed.impulse, 0.0f) );
+				break;
+//			case Gravity::GravityType_DirectedField:
+//				//this->gravity[i].directedField.
+//				//! TODO: @todo rethink
+//				break;
+			default: break;
+			}
+		}
+		(*proto)->SetState( state );
 
 		// Step 2: Apply Collision Response
 		this->worldScene.Visit( *proto, OnPossibleCollision );
@@ -213,6 +242,24 @@ void API_Impl::DestroyObject( const ICustomBody* objRef )
 	}
 }
 
+void API_Impl::AddGravity( const API::Gravity &g )
+{
+	this->gravity.push_back( g );
+}
+
+void API_Impl::RemoveGravity( const API::Gravity &g )
+{
+	for( ::std::vector<Gravity>::size_type i = this->gravity.size() - 1; i >= 0; --i )
+	{
+		if( g == this->gravity[i] )
+		{
+			int end = this->gravity.size() - 1;
+			this->gravity[i] = this->gravity[end];
+			this->gravity.resize( end );
+		}
+	}
+}
+
 //void API_Impl::ApplyForceAt( const ICustomBody* objRef, const Float3 &worldPos, const Float3 &worldF )
 //{
 //	unsigned int tempRef = this->worldScene.GetTemporaryReferenceOf( objRef );
diff --git a/Code/GamePhysics/Implementation/PhysicsAPI_Impl.h b/Code/GamePhysics/Implementation/PhysicsAPI_Impl.h
index 0c08bf11..314e0657 100644
--- a/Code/GamePhysics/Implementation/PhysicsAPI_Impl.h
+++ b/Code/GamePhysics/Implementation/PhysicsAPI_Impl.h
@@ -32,6 +32,9 @@ namespace Oyster
 			::Utility::DynamicMemory::UniquePointer<ICustomBody> ExtractObject( const ICustomBody* objRef );
 			void DestroyObject( const ICustomBody* objRef );
 
+			void AddGravity( const Gravity &g );
+			void RemoveGravity( const Gravity &g );
+
 			//void ApplyForceAt( const ICustomBody* objRef, const ::Oyster::Math::Float3 &worldPos, const ::Oyster::Math::Float3 &worldF );
 
 			//void SetMomentOfInertiaTensor_KeepVelocity( const ICustomBody* objRef, const ::Oyster::Math::Float4x4 &localI );
@@ -49,6 +52,7 @@ namespace Oyster
 		private:
 			::Oyster::Math::Float gravityConstant, updateFrameLength;
 			EventAction_Destruction destructionAction;
+			::std::vector<Gravity> gravity;
 			Octree worldScene;
 		};
 
diff --git a/Code/GamePhysics/PhysicsAPI.h b/Code/GamePhysics/PhysicsAPI.h
index 0904551d..019a4af7 100644
--- a/Code/GamePhysics/PhysicsAPI.h
+++ b/Code/GamePhysics/PhysicsAPI.h
@@ -22,6 +22,7 @@ namespace Oyster
 			struct SimpleBodyDescription;
 			struct SphericalBodyDescription;
 			struct CustomBodyState;
+			struct Gravity;
 		}
 
 		enum UpdateState
@@ -40,6 +41,7 @@ namespace Oyster
 		public:
 			typedef Struct::SimpleBodyDescription SimpleBodyDescription;
 			typedef Struct::SphericalBodyDescription SphericalBodyDescription;
+			typedef Struct::Gravity Gravity;
 
 			typedef void (*EventAction_Destruction)( ::Utility::DynamicMemory::UniquePointer<ICustomBody> proto );
 
@@ -124,6 +126,16 @@ namespace Oyster
 			 ********************************************************/
 			virtual void DestroyObject( const ICustomBody* objRef ) = 0;
 
+			/********************************************************
+			 * TODO: @todo doc
+			 ********************************************************/
+			virtual void AddGravity( const Gravity &g ) = 0;
+
+			/********************************************************
+			 * TODO: @todo doc
+			 ********************************************************/
+			virtual void RemoveGravity( const Gravity &g ) = 0;
+
 			///********************************************************
 			// * Apply force on an object.
 			// * @param objRef: A pointer to the ICustomBody representing a physical object.
diff --git a/Code/OysterPhysics3D/OysterPhysics3D.h b/Code/OysterPhysics3D/OysterPhysics3D.h
index 970d739e..f814ff46 100644
--- a/Code/OysterPhysics3D/OysterPhysics3D.h
+++ b/Code/OysterPhysics3D/OysterPhysics3D.h
@@ -273,6 +273,22 @@ namespace Oyster { namespace Physics3D
 			return momentOfInertia * angularImpulseAcceleration;
 		}
 
+		/******************************************************************
+		 * @todo TODO: doc
+		 ******************************************************************/
+		inline ::Oyster::Math::Float ForceField( ::Oyster::Math::Float g, ::Oyster::Math::Float massA, ::Oyster::Math::Float massB, ::Oyster::Math::Float radiusSquared )
+		{
+			return g * massA * massB / radiusSquared;
+		}
+
+		/******************************************************************
+		 * @todo TODO: doc
+		 ******************************************************************/
+		inline ::Oyster::Math::Float ForceField( ::Oyster::Math::Float g, ::Oyster::Math::Float massA, ::Oyster::Math::Float massB, const ::Oyster::Math::Float4 &deltaPos )
+		{
+			return g * massA * massB / deltaPos.Dot( deltaPos );
+		}
+
 		namespace MomentOfInertia
 		{ /// Library of Formulas to calculate moment of inerta for simple shapes
 			/** @todo TODO: add MomentOfInertia tensor formulas */