Hacking & Developing Keyboard is an Android keyboard developed by Philip Heyse that allows users to customize their typing experience. It features a full PC-keyboard layout with Ctrl, Alt, F1-F12, Esc, Tab, Page up/down, Home/End, Print, and Pause keys, as well as cursor keys and backward and forward delete. Additionally, a hidden suggestion area provides more space for typing.

Users can choose between regular, big, and round keys, and customize the keyboard's color from 16 million different options. The app also allows users to select a custom background image from their device or choose from one of 13 prepared looks.

For advanced users, the app provides the option to edit an XML file to create a personalized keyboard layout. The app also includes a demo version for testing, which is fully functional but adds the text "demo version" to each typed letter.

Overall, Hacking & Developing Keyboard is a versatile and customizable keyboard that caters to advanced users who want to optimize their typing experience.