There are three steps to the interview process (for interns, at least):

1. Basic phone interview. This is easy, a formality almost. They just chat, ask about your major, a project you've worked on, etc. Nothing to worry about.

2. Exam. This is the hardest part. It's a two-part exam, electronically proctored. One part contains a general 20-question exam measuring learning aptitude. All epic applicants have to take this, regardless of position. They give you a dummy (weird) programming language and teach it to you, then have you answer questions about it as you go. The second part, for programming applicants only, is just 4 interview-style programming questions that you type up in the language of your choice. This part required more mental stamina for me, so I would do this first and the other second, as you get to choose which to take first. I did not enjoy this part. This is also the part where most applicants seem to be weeded out.

3. On-site interview. This part was great. They fly you out to Madison, put you in a hotel for the night, have an employee take you to dinner, and ask all the questions you want. The next day is the actual interview day, where they take you on a tour around campus, have a session where they show you around their software, have you meet individually with a former intern, and feed you lunch. Very, very impressive, engaging campus. Lots of opportunities to ask questions. There are two interviews: one with an engineer who will discuss one of the projects you've done for a half hour or so, and then one with an HR representative who asks typical behavioral questions. Most people on Glassdoor say the on-site interview is easy and that you're basically guaranteed the position if you make it there, but I was not given an offer, so either that's not true or I did something wrong that I can't identify.

Tell me about a project you've worked on. (They then will try to find all the flaws in it.)