Tested on Chrome Version 47.0.2526.106 (64-bit), Firefox 40.0.3, Safari Version 9.0.2 (9537.86.3.9.1), and IE 11.18.105140.0 via Microsoft Remote Desktop (IE Tech Preview)
Click on the index.html to open up the page
In the app, click the thumbnail will open the lightbox. You can navigate the photos in the lightbox via clicking next and prev btns or by pressing the left and right arrow keys. You can close the lightbox by clicking greyed area or by pressing the escape key.