diff --git a/src/play_clj/g3d_physics.clj b/src/play_clj/g3d_physics.clj
index 339de9b..921ce3f 100644
--- a/src/play_clj/g3d_physics.clj
+++ b/src/play_clj/g3d_physics.clj
@@ -17,7 +17,7 @@
             btSoftRigidDynamicsWorld]
            [play_clj.g3d_physics ContactListener3D]))
 
-(def ^:private init (delay (Bullet/init)))
+(def init-bullet (delay (Bullet/init)))
 
 (defrecord World3D [object])
 (defrecord Body3D [object])
@@ -50,7 +50,7 @@
 
 (defn bullet-3d*
   [type]
-  @init
+  @init-bullet
   (case type
     :rigid (discrete-dynamics)
     :soft-rigid (soft-rigid-dynamics)
diff --git a/src/play_clj/physics.clj b/src/play_clj/physics.clj
new file mode 100644
index 0000000..8844d76
--- /dev/null
+++ b/src/play_clj/physics.clj
@@ -0,0 +1,179 @@
+(ns play-clj.physics
+  (:require [play-clj.g2d-physics :as p2d]
+            [play-clj.g3d-physics :as p3d]
+            [play-clj.utils :as u])
+  (:import [com.badlogic.gdx.physics.box2d Body World]
+           [play_clj.g3d_physics Body3D World3D]))
+
+; this namespace is for internal use only. you should use the g2d-physics and
+; g3d-physics namespaces directly, instead.
+
+(defmulti add-body!
+  (fn [screen body] (-> screen (u/get-obj :world) class)))
+
+(defmethod add-body!
+  World
+  [screen b-def]
+  (p2d/add-body! screen b-def))
+
+(defmethod add-body!
+  World3D
+  [screen body]
+  (p3d/add-body! screen body))
+
+(defmulti body-position!
+  (fn [entity a1 a2 a3] (-> entity (u/get-obj :body) class)))
+
+(defmethod body-position!
+  Body
+  [entity x y angle]
+  (p2d/body-position! entity x y angle))
+
+(defmethod body-position!
+  Body3D
+  [entity x y z]
+  (p3d/body-position! entity x y z))
+
+(defmulti body-x!
+  (fn [entity x] (-> entity (u/get-obj :body) class)))
+
+(defmethod body-x!
+  Body
+  [entity x]
+  (p2d/body-x! entity x))
+
+(defmethod body-x!
+  Body3D
+  [entity x]
+  (p3d/body-x! entity x))
+
+(defmulti body-y!
+  (fn [entity y] (-> entity (u/get-obj :body) class)))
+
+(defmethod body-y!
+  Body
+  [entity y]
+  (p2d/body-y! entity y))
+
+(defmethod body-y!
+  Body3D
+  [entity y]
+  (p3d/body-y! entity y))
+
+(defmulti body-z!
+  (fn [entity z] (-> entity (u/get-obj :body) class)))
+
+(defmethod body-z!
+  Body3D
+  [entity z]
+  (p3d/body-z! entity z))
+
+(defmulti body-angle!
+  (fn [entity angle] (-> entity (u/get-obj :body) class)))
+
+(defmethod body-angle!
+  Body
+  [entity angle]
+  (p2d/body-angle! entity angle))
+
+(defmulti first-entity
+  (fn [screen entities] (-> screen (u/get-obj :world) class)))
+
+(defmethod first-entity
+  World
+  [screen entities]
+  (p2d/first-entity screen entities))
+
+(defmethod first-entity
+  World3D
+  [screen entities]
+  (p3d/first-entity screen entities))
+
+(defmulti second-entity
+  (fn [screen entities] (-> screen (u/get-obj :world) class)))
+
+(defmethod second-entity
+  World
+  [screen entities]
+  (p2d/second-entity screen entities))
+
+(defmethod second-entity
+  World3D
+  [screen entities]
+  (p3d/second-entity screen entities))
+
+(defmulti add-joint!
+  (fn [screen joint] (-> screen (u/get-obj :world) class)))
+
+(defmethod add-joint!
+  World
+  [screen j-def]
+  (p2d/add-joint! screen j-def))
+
+(defmulti step!
+  (fn [screen & [entities]] (-> screen (u/get-obj :world) class)))
+
+(defmethod step!
+  World
+  [screen & [entities]]
+  (p2d/step! screen entities))
+
+(defmethod step!
+  World3D
+  [screen & [entities]]
+  (p3d/step! screen entities))
+
+(def box-2d* p2d/box-2d*)
+(defmacro box-2d [& body] `(p2d/box-2d ~@body))
+(defmacro box-2d! [& body] `(p2d/box-2d! ~@body))
+(defmacro body-def [& body] `(p2d/body-def ~@body))
+(defmacro body! [& body] `(p2d/body! ~@body))
+(defmacro joint-def [& body] `(p2d/joint-def ~@body))
+(defmacro joint! [& body] `(p2d/joint! ~@body))
+(defmacro fixture-def [& body] `(p2d/fixture-def ~@body))
+(defmacro fixture! [& body] `(p2d/fixture! ~@body))
+
+(def chain-shape* p2d/chain-shape*)
+(defmacro chain-shape [& body] `(p2d/chain-shape ~@body))
+(defmacro chain-shape! [& body] `(p2d/chain-shape! ~@body))
+(def circle-shape* p2d/circle-shape*)
+(defmacro circle-shape [& body] `(p2d/circle-shape ~@body))
+(defmacro circle-shape! [& body] `(p2d/circle-shape! ~@body))
+(def edge-shape* p2d/edge-shape*)
+(defmacro edge-shape [& body] `(p2d/edge-shape ~@body))
+(defmacro edge-shape! [& body] `(p2d/edge-shape! ~@body))
+(def polygon-shape* p2d/polygon-shape*)
+(defmacro polygon-shape [& body] `(p2d/polygon-shape ~@body))
+(defmacro polygon-shape! [& body] `(p2d/polygon-shape! ~@body))
+
+(def bullet-3d* p3d/bullet-3d*)
+(defmacro bullet-3d [& body] `(p3d/bullet-3d ~@body))
+(defmacro bullet-3d! [& body] `(p3d/bullet-3d! ~@body))
+(def rigid-body* p3d/rigid-body*)
+(defmacro rigid-body [& body] `(p3d/rigid-body ~@body))
+(defmacro rigid-body! [& body] `(p3d/rigid-body! ~@body))
+(def rigid-body-info p3d/rigid-body-info)
+(def soft-body* p3d/soft-body*)
+(defmacro soft-body [& body] `(p3d/soft-body ~@body))
+(defmacro soft-body! [& body] `(p3d/soft-body! ~@body))
+(def soft-body-info p3d/soft-body-info)
+
+(def box-shape* p3d/box-shape*)
+(defmacro box-shape [& body] `(p3d/box-shape ~@body))
+(defmacro box-shape! [& body] `(p3d/box-shape! ~@body))
+(def capsule-shape* p3d/capsule-shape*)
+(defmacro capsule-shape [& body] `(p3d/capsule-shape ~@body))
+(defmacro capsule-shape! [& body] `(p3d/capsule-shape! ~@body))
+(def cone-shape* p3d/cone-shape*)
+(defmacro cone-shape [& body] `(p3d/cone-shape ~@body))
+(defmacro cone-shape! [& body] `(p3d/cone-shape! ~@body))
+(def cylinder-shape* p3d/cylinder-shape*)
+(defmacro cylinder-shape [& body] `(p3d/cylinder-shape ~@body))
+(defmacro cylinder-shape! [& body] `(p3d/cylinder-shape! ~@body))
+(def sphere-shape* p3d/sphere-shape*)
+(defmacro sphere-shape [& body] `(p3d/sphere-shape ~@body))
+(defmacro sphere-shape! [& body] `(p3d/sphere-shape! ~@body))
+
+(defn init-bullet!
+  []
+  @p3d/init-bullet)