<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
    xmlns:s="library://ns.adobe.com/flex/spark"
    xmlns:mx="library://ns.adobe.com/flex/halo">

    <fx:Script>
        import spark.effects.animation.RepeatBehavior;
        private var animating:Boolean = false;
    </fx:Script>
    <fx:Declarations>
        <s:GlowFilter id="glow" blurX="20" blurY="20" />
        <s:AnimateFilter id="glower" target="{button}" 
                bitmapFilter="{glow}" duration="600"
                repeatCount="0" repeatBehavior="{RepeatBehavior.REVERSE}">
            <s:SimpleMotionPath property="alpha" valueFrom="0" valueTo="1"/>
        </s:AnimateFilter>
    </fx:Declarations>
    
    <s:Button id="button" x="100" y="100" height="40"
        mouseOver="if (!animating) { glower.play(); animating = true}" 
        mouseOut="if (animating) { glower.end(); animating = false}"/>    
        
</s:Application>