localStorage. With this, anyone can create content in a "mnemonic medium" like the above two articles. Authors don't need to write code or use a third-part server, and users don't need to download apps. Ideally, I wanted to build and as standard HTML custom elements - which would have been easier to use, and also allowed questions and answers to be arbitrary HTML (pictures, math, audio or video clips etc), but due to the limitations of VueJS and WebComponents, this is the best I could do for now. Improvements are welcome!