arm_sim.launch.py is the main (and only so far) launch file of the project. It is rather simple: as this is the first project in "robotic arm" series, I have removed all command line parameters, using hardcoded values to make it simpler.
Running this launch file with joint_state_publisher_gui uncommented, will produce the following:
With joint_state_publisher_gui commented out, the result will be the same, of course, except the window with controls will not show up.