I often write code on the go (for e.g. on bus rides), mainly prototyping ideas as single-page HTML/CSS/JS. I’ve used code editor apps as well as developer keyboards on mobile phones, but none of them really clicked for me. So I built something for myself: a simple browser-based code editor, optimized specifically for mobile devices. It lives at https://me.cmdr2.org/carbon (GitHub repo), runs entirely in the browser, and stores your work locally.