next (hard) {
		if (!hard && _.items.length) {
			_.nextItem();
		}
		else {
			_.goto(_.index + 1);

			_.item = 0;

			// Mark all items as not displayed, if there are any
			_.items.forEach(item => item.classList.remove("displayed", "current"));
		}
	}
@param hard {Boolean} Whether to advance to the next slide (true) or
			just the next step (which could very well be showing a list item)