https://www.youtube.com/watch?v=bQHXFO1A5b0I have been using <details><summary>hello</summary>popup</details> while reading on my Android phone using one of their reader programs Lithium. It is responsive and trouble free so far. The only other kind of popup that I am familiar with is is <hover>popup</hover>. It requires a light touch and also will not stay open, whereas details does stay open. If it works even if it is not supposed to work, is there any reason not to use it?
Best regards, Pop