Is there a copyright on the functionality of the site?

Question

Copyright

Good afternoon, I have a question about the copyright on the functionality of the site.
Now I work in a team that is creating a ticket booking service. The site https://www.agent.ru/ has an analogue of similar functionality, although the service will also provide specific functionality.
One of our team members left the company and as I recently found out he works in another team where they create a similar service. The question is whether he can be held legally liable for copyright infringement, for deciding to implement our project on the side? It is clear that in their implementation version there will be a different design and they will also most likely rewrite the program code, the name of the project will also be different.

Answer 1

If it does not use the developments of your service (which cannot be proven) and the implementation is not patented, then you cannot do anything.
Copyright does not apply to an abstract idea.

Answer 2

so far, I see that he decided to implement their project on the side.