I am booking train tickets for a trip in Sri Lanka through the official government website. The website is giving me the default option of "Air Conditioned Saloon" which I believe is first class.

I want to book second class because I do not like AC and because I find the scenic experience of the journey more direct and pleasant through an open window.
However I can not figure out how to select second class tickets in the web interface. Am I missing something, or are second class tickets simply not available through the website?