#HTML #js #css #docs 如何创建分屏
[html - Split in half vertically and horizontally second flex item - Stack Overflow](https://stackoverflow.com/questions/49550792/split-in-half-vertically-and-horizontally-second-flex-item)
[How To Create a Two Column Layout](https://www.w3schools.com/howto/howto_css_two_columns.asp)
[How To Create A Split Screen](https://www.w3schools.com/howto/howto_css_split_screen.asp)
[Split.js](https://split.js.org/)
🤔今天才知道 CSS flexbox 不是用来创建 responsive 的，只是可以创建随意缩放而良好排版的嵌套盒
responsive 要靠 @media 指定覆盖条件，浏览器支持好

https://stackoverflow.com/questions/6014702/how-do-i-detect-shiftenter-and-generate-a-new-line-in-textarea 这个用 Selection/Keyboard API
<hr> <label> 这些标签和 resize, outline 的CSS熟悉 都是新学的啊，看来还是得做了才知道。