There are many programming languages but one that I know is sutable for programming on mobile. I am talking about DroidScript. It is used mainly in robotics but have also other large capabilities. For larger projects it is racommended using the build in browser based IDE editor. It connects via wifi to your device alowing wire free coding from Windows, Linux or Mac pcs. DroidScript is easy to use but not just for beginners, as well for professionals and building commercial applications. DroidScript is industry standard Javascript, so they are compatible. You can insert some parts of droid script into HTML code.