Great html dungeon! I'll have to take a look at the source to see if i can improve my own html work.
(to be clear, it's also a good dungeon, not just a decent implementation of html)
Have you considered an epub version? Super-easy to convert html to epub (you almost certainly know that Calibre is a free program that can do it for you) and would allow easy offline use.
Maybe one day itch will finally allow paywalls on "run in browser" content -- i think it's a major barrier to tRPG people embracing html.