Nucleus is a plain-text editor hidden in a bookmarklet. It is fully responsive and supports all HTML5-supporting browsers. Nucleus is ultra-lightweight - it doesn't support any formating at all and saves itself along with your files when you save it. You can save Nucleus documents in PDF format by utilising the print-to-PDF functionality of your browser. It is also fully customizable and open-source - simply change the source code.
https://gist.github.com/clisamurai/1f355b6028c8b9d1836b4ca01f173244 by Mitchell Palmer
I replaced his styles with Nanoreset to save some space, and stripped out explanatory text. I also simplified and modernized the JavaScript portion.
- An HTML5, ES6/ES2015 compliant web browser