Meanwhile, the Internet Archive's trove of old Mac software that runs in your browser is growing by the week. Lots of Hypercard stacks already in there, e.g. https://archive.org/details/TheManholeMacintosh
Only problem with the Archive.org setup is that you need to use System 6.0.* or really early System 7 to get the animation timing correct. The slow and sluggish frame by frame animation with later System versions is so annoying and ruining my childhood memories ;D