Thanks for checking it out!
You're right that a browser-based app is not the same thing. At the same time, as an individual maintaining this entire thing, I can't invest the time and effort to port this to multiple platforms, whereas this format enables it to be used by people on (self-reported) laptops, tablets, as well as desktops.
It doesn't have to be on multiple platforms though...
One of the cool things about Hypercard was that it could access the entire machine. A sandboxed browser page will never (hopefully) be able to do that.
