It's rough not finishing what you wanted, but I think you got more done than you think. Having the interactable desktop and system to take in commands is helpful, but your next steps should be parsing user input to trigger those commands and then thinking about how to integrate those commands into a tower defense system.
The most common case would be rival hackers or police trying to 'hack back' at your Router, so you would run commands to add firewalls, move your hacking services from one service to another, defend your ports. Just take it one feature at a time and build up to that with the focus being on making the player feel like a genius.