diff --git a/src/play_clj/core.clj b/src/play_clj/core.clj
index b508eb9..f145003 100644
--- a/src/play_clj/core.clj
+++ b/src/play_clj/core.clj
@@ -1,7 +1,5 @@
 (ns play-clj.core
-  (:require [clojure.set :as set]
-            [play-clj.g2d-physics :as g2dp]
-            [play-clj.utils :as u])
+  (:require [play-clj.utils :as u])
   (:import [com.badlogic.gdx Application Audio Files Game Gdx Graphics Input
             InputMultiplexer InputProcessor Net Screen]
            [com.badlogic.gdx.graphics Camera Color GL20 OrthographicCamera
diff --git a/src/play_clj/core_graphics.clj b/src/play_clj/core_graphics.clj
index 99a8c4b..b99b9aa 100644
--- a/src/play_clj/core_graphics.clj
+++ b/src/play_clj/core_graphics.clj
@@ -234,25 +234,6 @@
     (render! screen)
     (draw! screen entities)))
 
-; physics
-
-(defn step!
-  ([{:keys [world time-step velocity-iterations position-iterations]
-     :or {time-step (/ 1 60) velocity-iterations 10 position-iterations 10}}]
-    (assert world)
-    (cond
-      (isa? (type world) World)
-      (.step ^World world time-step velocity-iterations position-iterations)))
-  ([screen entities]
-    (step! screen)
-    (map (fn [entity]
-           (if-let [body (:body entity)]
-             (assoc entity
-                    :x (g2dp/body-x body)
-                    :y (g2dp/body-y body))
-             entity))
-         entities)))
-
 ; cameras
 
 (defn orthographic*
diff --git a/src/play_clj/g2d_physics.clj b/src/play_clj/g2d_physics.clj
index ae8019c..e8c95a4 100644
--- a/src/play_clj/g2d_physics.clj
+++ b/src/play_clj/g2d_physics.clj
@@ -164,7 +164,7 @@
   [object k & options]
   `(u/call! ^PolygonShape ~object ~k ~@options))
 
-; misc functions
+; misc
 
 (defmacro contact!
   [object k & options]
@@ -193,3 +193,20 @@
       (-> contact .getFixtureB .getBody)))
   ([screen entities]
     (find-body (second-contact screen) entities)))
+
+(defn step!
+  ([{:keys [world time-step velocity-iterations position-iterations]
+     :or {time-step (/ 1 60) velocity-iterations 10 position-iterations 10}}]
+    (assert world)
+    (cond
+      (isa? (type world) World)
+      (.step ^World world time-step velocity-iterations position-iterations)))
+  ([screen entities]
+    (step! screen)
+    (map (fn [entity]
+           (if-let [body (:body entity)]
+             (assoc entity
+                    :x (body-x body)
+                    :y (body-y body))
+             entity))
+         entities)))