update() {

		// Update progress if enabled
		if( this.Reveal.getConfig().progress && this.bar ) {

			let scale = this.Reveal.getProgress();

			// Don't fill the progress bar if there's only one slide
			if( this.Reveal.getTotalSlides() < 2 ) {
				scale = 0;
			}

			this.bar.style.transform = 'scaleX('+ scale +')';

		}

	}
Updates the progress bar to reflect the current slide.