*scratch*.el

diff --git a/src/frame-manager.lisp b/src/frame-manager.lisp
index b0b3e7c..c954c46 100644
--- a/src/frame-manager.lisp
+++ b/src/frame-manager.lisp
@@ -1,7 +1,8 @@
 (in-package :box.frame)
 
 (defclass frame-manager ()
-  ((%start :initform (local-time:now))
+  ((%vsyncp :initarg :vsyncp)
+   (%start :initform (local-time:now))
    (%now :initform (local-time:now))
    (%before :initform 0)
    (%total-time :reader total-time
@@ -45,7 +46,7 @@
     (incf %frame-time %delta-buffer)
     (let ((frame-count (truncate (1+ (* %frame-time refresh-rate))))
           (previous %frame-time))
-      (setf frame-count (if (minusp frame-count) 1 frame-count)
+      (setf frame-count (if (<= frame-count 0) 1 frame-count)
             %frame-time (/ frame-count refresh-rate)
             %delta-buffer (- previous %frame-time)))))
 
@@ -90,12 +91,13 @@ or perform operations periodically, rather than every game tick."
   "This is designed to be called each iteration of a main game loop, which calls STEP-FUNC to update
 the physics when necessary, based on the DELTA of the frame manager. PERIODIC-FUNC is a function to
 be called periodically, controlled by the PERIOD-INTERVAL slot of FRAME-MANAGER."
-  (with-slots (%init %now %start %before %total-time %frame-time %period) frame-manager
+  (with-slots (%vsyncp %init %now %start %before %total-time %frame-time %period) frame-manager
     (setf %before %now
           %now (local-time:now)
-          %frame-time (local-time:timestamp-difference %now %before)
-          %total-time (local-time:timestamp-difference %now %start))
-    (smooth-delta-time frame-manager refresh-rate)
+          %frame-time (float (local-time:timestamp-difference %now %before) 1.0)
+          %total-time (float (local-time:timestamp-difference %now %start) 1.0))
+    (when %vsyncp
+      (smooth-delta-time frame-manager refresh-rate))
     (update frame-manager step-func)
     (when periodic-func
       (periodic-update frame-manager periodic-func))