diff --git a/syndicate/examples/gl-2d-platformer.rkt b/syndicate/examples/gl-2d-platformer.rkt
index c96910d..fb35655 100644
--- a/syndicate/examples/gl-2d-platformer.rkt
+++ b/syndicate/examples/gl-2d-platformer.rkt
@@ -519,15 +519,20 @@
          (play-sound-sequence 270318)
          (update-piece! g pos jump-vel)))
 
-   (on (message (inbound (inbound (frame-event $counter _ $elapsed-ms _))))
-       (when (zero? (modulo counter 10))
-         (log-info "Instantaneous frame rate at frame ~a: ~a Hz"
-                   counter
-                   (/ 1000.0 elapsed-ms)))
-       (previous-positions (positions))
-       (previous-velocities (velocities))
-       (for [((id g) (in-hash (configs))) #:when (game-piece-has-attribute? g 'mobile)]
-         (update-game-piece! elapsed-ms id)))))
+   (define start-time #f)
+   (on (message (inbound (inbound (frame-event $counter _ _ _))))
+       (let ((stop-time (current-inexact-milliseconds)))
+         (when (not (eq? start-time #f))
+           (define elapsed-ms (- stop-time start-time))
+           (when (zero? (modulo counter 10))
+             (log-info "Instantaneous frame rate at frame ~a: ~a Hz"
+                       counter
+                       (/ 1000.0 elapsed-ms)))
+           (previous-positions (positions))
+           (previous-velocities (velocities))
+           (for [((id g) (in-hash (configs))) #:when (game-piece-has-attribute? g 'mobile)]
+             (update-game-piece! elapsed-ms id)))
+         (set! start-time stop-time)))))
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; Player