MAD

MAD stands for Mobile App Development. It allows you to develop apps or games on your mobile phone. You don't need anything else, although bluetooth keyboard may improve your typing speed. It also works offline. Target audience of this app are web developers. You need to know HTML, JS, CSS to make apps.

When you finish your app you can publish it for others to try and you can see apps created by others. If creator allows it apps can be forked - it creates copy of app in your phone and you can locally modify it.