Funny story actually, there were a few other engineers but not very much collaboration. They were resistant to sharing source code or algorithm details, so I had to essentially reverse engineer how their other products worked. I was good enough at it that I came up with several features they didn't know were possible. They eventually ended up letting me go and cloned my design, which I thought was weird, but it was developed for them in the first place so not a big deal.
The lengths to which devs will go not to collaborate.