I am a bit obsessed with this topic and have already implementd various stabs at a "fix" (in different stages of completion):

1. "Tidej" -- a mobile JS IDE: https://tidejnet.appspot.com/v3/ -- Too complex, too little guidance, code editor used not really mobile friendly, browser seems even less usable than native for this purpose.

2. "Flowgrid" -- a dataflow IDE for Android: http://flowgrid.org -- turns out drawing is even harder than typing on mobile

3. "CodeChat" -- a strange not quite smalltalk dialect with a chat-like interface: https://github.com/stefanhaustein/codechat -- I can't fully remember the syntax myself -- perhaps a bit too ambitioned.

4. "ASDE" -- The "current" approach: https://m.youtube.com/watch?v=0pQ5PU91Ils -- the main idea is that line numbers will help the to avoid the biggest pain on mobile: fiddely cursor positionong. Hope this one will pan out better than the others...