Edit: You can now preview the changes live. Also, the pull request got accepted!

I just submitted a GitHub PR for adding multilingual support to Mozilla’s HTML5 Sandstone slidedeck. The selection is persistent across slide changes, and in Firefox, the URL bar will update the lang attribute as well.

Pictures are worth thousands of words, so here you go:

To add languages:

1. Add the style tags to the stylesheet
2. Modify the language menu
3. Place your translation within
   tags with language code class names

Example code:

https://garykwong.wordpress.com/2015/08/12/multilingual-slides-in-html5-mozilla-sandstone-slidedeck/