[Plugin] Shake Plugin

     if(runShake){
               // Get all instances with this behavior
               var all = this.behavior.my_instances.values();
               var sumx = 0, sumy = 0;
               var i, len;
               
               for (i = 0, len = all.length; i < len; i++)
               {
                    sumx += all[i].x;
                    sumy += all[i].y;
               }
               
               var layout = this.inst.layer.layout;
               
               // Is in a shake?
               var now = this.runtime.kahanTime.sum;
               var offx = 0, offy = 0;
               
               if (now >= this.behavior.shakeStart && now < this.behavior.shakeEnd)
               {
                    var mag = this.behavior.shakeMag * Math.min(this.runtime.timescale, 1);
                    
                    // Mode 0 - reducing magnitude - lerp to zero
                    if (this.behavior.shakeMode === 0)
                         mag *= 1 - (now - this.behavior.shakeStart) / (this.behavior.shakeEnd - this.behavior.shakeStart);
                         
                    var a = Math.random() * Math.PI * 2;
                    var d = Math.random() * mag;
                    offx = Math.cos(a) * d;
                    offy = Math.sin(a) * d;
               }
               
               layout.scrollToX((sumx / all.length + offx)+xOffset);
               layout.scrollToY((sumy / all.length + offy)+yOffset);          
          }