:-D I’m the developer of this, and particularly proud that not only can you Import stacks, icons and all, but you can Export single page web apps that end in .stack.html and run in any modern browser! It’s all in the hamburger menu.

One issue is the HyperCard fit holistically with Macs of the 80s and early 90s. A straight clone doesn't quite make sense today -- perhaps we need slightly different metaphors.

Last year I was a part of a research team that explored some of this. We ended up producing a system called Simpletalk [1], which is essentially a web-based system and scripting language inspired by Smalltalk and Hypercard. If you are interested, I also gave a talk [2] on some of the motivations and design behind the system.

[1] https://github.com/dkrasner/Simpletalk

[2] https://www.youtube.com/watch?v=5U6MkU5fLJw

This isn't because people just ignored or forgot Hypercard - similar tools just evolved in many different directions and many of them were much more popular than Hypercard. FileMaker, Access, Visual Basic and their ilk come to mind; the current crop of 'no code' tools are also distant descendants. A key difficulty isn't replicating the UI, it's coming up with a tool/system that's both accessible to non-experts while also providing a smooth 'power curve' to the more sophisticated features of the platform. Without that, motivated beginners quickly run up against the limitations of the built-in functionality or a big jump in conceptual and practical complexity.