1. The app uses MVP design pattern
2. A custom JoystickView simulates a lever-based joystick interface
3. Joystick positions are normalized with values between -100 and 100
4. Joystick continuous "position hold" functionality implemented using a dedicated HandlerThread
5. Asynchronous Bluetooth communication is implemented using RxJava
6. Test Driven Development practices were applied while overhauling the old version of this app
7. Added ability to send custom commands to the rover (currently only supports "_off" for safe rover shutdown)

This is a basic Android App which controls Raspberry Pi W-based rover.
It communicates over standard Bluetooth sockets using Serial Port Profile.
A custom JoystickView serves as a user input mechanisms to control the rover. The JoystickView takes the handle position and translates it into control input. The X and Y coordinates specify direction, while the distance from the center specifies the motor speed.

The directional and control commands are sent in a specially-formatted string over the the serial Bluetooth connection. The Python script on the Pi side seeks out valid commands using regular expressions, parses the input and activates appropriate GPIO pins See python page.