diff --git a/.gitignore b/.gitignore
index 114e85a..93af298 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,8 +1,17 @@
-/pom.xml
-*jar
-/lib
-/classes
-/native
-/.lein-failures
-/checkouts
-/.lein-deps-sum
+# Taken from Github recommended gitignore file for Leiningen.
+# https://raw.githubusercontent.com/github/gitignore/master/Leiningen.gitignore
+# https://github.com/github/gitignore/blob/master/Leiningen.gitignore
+
+pom.xml
+pom.xml.asc
+*.jar
+*.class
+/lib/
+/classes/
+/target/
+/checkouts/
+.lein-deps-sum
+.lein-repl-history
+.lein-plugins/
+.lein-failures
+.nrepl-port
diff --git a/project.clj b/project.clj
index 2d59ee1..ee17bb8 100644
--- a/project.clj
+++ b/project.clj
@@ -5,4 +5,9 @@
 
   :main quilltest.balls
 
-  :warn-on-reflection true)
+  ;; :warn-on-reflection true
+  ;; DEPRECATED: https://github.com/technomancy/leiningen/blob/master/sample.project.clj
+  
+  :global-vars {*warn-on-reflection* true}
+  
+  )
diff --git a/src/quilltest/physics.clj b/src/quilltest/physics.clj
index 8dddce7..d2af8dc 100644
--- a/src/quilltest/physics.clj
+++ b/src/quilltest/physics.clj
@@ -50,20 +50,27 @@
 
 (defrecord RigidBody [mass position velocity])
 
+
 (defn approaching [r1 r2]
   (let [v1 (:velocity r1)
-        v2 (:velocity r2)]
-    (with-math (neg? (* v1 v2)))))
+        v2 (:velocity r2)
+        x1 (:position r1)
+        x2 (:position r2)]
+    (with-math (neg? (* (- x1 x2) (- v1 v2))))))
 
-(defn colliding? [r1 r2]
-  (and (approaching r1 r2)
+
+(defn distance [r1 r2]
     (let [x1 (:position r1)
           x2 (:position r2)
           [x1 y1] [(:x x1) (:y x1)]
           [x2 y2] [(:x x2) (:y x2)]
-          [dx dy] [(- x1 x2) (- y1 y2)]
-          distance (Math/sqrt (+ (* dy dy) (* dx dx)))]
-      (< distance 20))))
+          [dx dy] [(- x1 x2) (- y1 y2)]]
+      (Math/sqrt (+ (* dy dy) (* dx dx)))))
+
+
+(defn colliding? [r1 r2]
+  (and (approaching r1 r2)
+      (< (distance r1 r2) 20)))
 
 (defn collide
   "Elastically collides two rigid bodies, returning