Except TextNut, I am the creator of geniuswiki, an open source web-based WIKI software. You may know markup writing is the fundamental concept of WIKI. Definitely, I am a markup (not only Markdown) writing enthusiast. That is why I made TextNut.
TextNut is my first OS X application. My major expertise is web development. Geniuswiki is a Java based web system. In my current startup, I am in charge of the full stack production line. The small part is written by Java, C and Golang. Most is Python based. For front end, I use AngularJS, BootStrap, Jquery etc. In backend, I heavily adopt Python, Django, Redis, MongoDB and MySQL. More than that, I manage 10+ Amazon EC2 servers which are running various services for internal an external purpose.
My technical radar is expanding to Swift, Rust and Docker, I hope have chance to use them in my next project.