Their recruiter contacted me via email. After answering some questions over email, the recruiter got back to me saying she wanted to schedule a phone screen interview. Had a phone screen interview with someone who is considered a peer. He was a project manager which i thought was odd but as long as you can come up with an idea to to make their game better and explain it, you should get through. I thought I would be chatting with the hiring manager but that wasn't the case.
If you pass that, after a couple of days, I got contacted by the recruiter again to set up a 4 hour block for onsite interviews. I met with 5 total. Two of the interviews were brainstorming sessions. One asked to design a weight loss app. Another asked to come up with four trending topics and give two examples of products for each topic that are the best examples and why. Then after that, she asked to mash up two of them and come up with a product idea.
Nothing to really prep for. You either know the space or you don't.