diff --git a/samples/bounce.scm b/samples/bounce.scm
index 4543a4c..b42298d 100644
--- a/samples/bounce.scm
+++ b/samples/bounce.scm
@@ -29,10 +29,10 @@
 					    ((if (circle-2d-filled? circle)
 						 draw-circle
 						 draw-circle-lines)
-					     (v-x draw-pos)
-					     (v-y draw-pos)
+					     (inexact->exact (round (v-x draw-pos)))
+					     (inexact->exact (round (v-y draw-pos)))
 					     (circle-2d-radius circle)
-					     (visual-2d-color vis-2d))))))))))
+					     (use-color (visual-2d-color vis-2d)))))))))))
 
 
 (define-record-type <rigidbody-2d>
@@ -134,11 +134,11 @@
 	   (vec 5 1)
 	   (make-color 0 0 1 1))
 
-(make-ball (vec 300 300)
+(make-ball (vec 200 200)
 	   (vec -2 -2)
 	   (make-color 0 1 0 1))
 
-(make-ball (vec 600 600)
+(make-ball (vec 300 300)
 	   (vec -2 -2)
 	   (make-color 1 0 0 1))