I have no idea what could be causing that. I don't think that error can be directly caused by my game (I don't have a function called "detectStore" anywhere in my own code or dependencies), but after some googling it looks like similar errors can be caused by the browser extension "Honey" conflicting with page content (not sure why that would affect the bookstacks room in particular, though). Do you have that installed and/or did it say the error was produced by a file called `h1-check.js`? Maybe try disabling browser extensions?
In any case, sorry about the bug & sorry for all the questions! No need to keep helping with the troubleshooting if you don't want to. hankworx above suggests downloading via the itch app (or maybe try another browser?) if you still want to play it.
Never mind, I think you're right that this error is unrelated (but probably still caused by an extension). Problem has something to do with PNG gamma correction; see my response to hankworx above. Hopefully I'll be allowed to upload a fix at some point. In any case, thanks for helping provide information!