fix error with multiple decimal em in safari

css/reveal.css

@@ -272,8 +272,8 @@ body {
     border-radius: 0.25em;
     background-color: currentColor;
     transition: all 0.15s ease, background-color 0.8s ease;
-    -webkit-transform-origin: 0.25em 50%;
-            transform-origin: 0.25em 50%;
+    -webkit-transform-origin: 0.2em 50%;
+            transform-origin: 0.2em 50%;
     will-change: transform; }
   .reveal .controls .controls-arrow {
     position: relative;

css/reveal.scss

@@ -314,7 +314,7 @@ $controlsArrowAngleActive: 36deg;
 		background-color: currentColor;
 
 		transition: all 0.15s ease, background-color 0.8s ease;
-		transform-origin: $controlArrowThickness/2 50%;
+		transform-origin: floor(($controlArrowThickness/2)*10)/10 50%;
 		will-change: transform;
 	}