this.selectedBlobMoveTo = function(x, y)
      {
        if(this.selectedBlob == null)
        {
          return; 
        }
        this.selectedBlob.moveTo(x, y); 
      }
      
      this.move = function(dt)
      {
        var i; 
        
        for(i = 0; i < this.blobs.length; i++)
        {
          if(this.blobs[i] == null)
          {
            continue; 
          }
          this.blobs[i].move(dt); 
        }
      }