Big waste of time - don't bother.
I applied back in January 2016. They didn't respond until April of 2016. Took several weeks after each step to get back to me. They're very slow.
2 Phone interviews
Standard stuff, asking why Sledgehammer, about my background etc. Basic Screening.
Coding challenge
Standard as well, except extremely long. They had 10 written answers, 1 moderate challenge and 1 difficult challenge. Took quite a bit longer than other companies.
Whiteboard coding challenge
This was pretty easy. Worked with some other candidates to solve and identify a problem. I believe it was more to see how you would work with the team and communicate with others, not so much of a technical challenge.
Interview Panel
Asked lots of questions. Some google style questions that everyone knows doesn't mean anything. Some of the people that were asking about my position didn't even know what they were talking about, seemed like HR type of people so not sure why the engineers weren't asking those questions.
I received an offer that was a good $20-$40k less than what I was already making. Based on the reviews on the company, I knew they weren't paying as much, but I didn't know it would be that bad. Apparently they give you bonuses based on the number of games they sell. Many people say that the bonuses aren't that big, and if you're shipping one game every 3 years, that's not a lot of bonuses.
Obviously declined the offer, since they aren't even paying what I'm getting now. I don't know how much people work here, but from what I gathered as well, lots of them are working on weekends and since it's salary you won't get any overtime.
tl;dr - don't bother with this place. They don't pay well and you'll be working out of the wazoo.