Line drawing is a bit messy to understand. You must click on a white border of the frame, hold the click & release it on another white border. If you still can't get it you could watch one of the videos posted below.
This is a student project and our team does not plan to work more on it. We had a hard time making the controls as easy to use as possible. Adding gamepad support would be inefficient with line drawing & erasing without a complete rework of the system. So it's not going to happen I'm sorry.