ch slide change to the browser history
        history: true,

        // Enable keyboard shortcuts for navigation
        keyboard: true,

        // Enable the slide overview mode
        overview: true,

        // Disables the default reveal.js slide layout (scaling and centering)
        // so that you can use custom CSS layout
        disableLayout: false,

        // Vertical centering of slides
        center: false,

        // Enables touch navigation on devices with touch input
        touch: tru