Saw IXL at a career fair at my university and got an interview on campus the next day (had to upload my resume to their website before then--the cover letter was optional). The interview itself was pretty laid back, and my interviewer and I hit it off really well personality-wise. There was a role play part, in which I had to explain what the domain of a function is to an 8th grader and a brain teaser (the jelly bean one everyone is referring to). After less than a couple of weeks, I got an e-mail about scheduling a phone interview. Mine was with someone who was working for the same position I was applying for, and it turned out she had a math Ph.D. in the same field I work in. Well, unfortunately, a lot of math Ph.D.s are a little awkward, and this phone conversation suffered a bit for it--there were some of those awkward silences that other people have mentioned, although not that many. It didn't help that my interviewer wasn't a native speaker and spoke with a thick accent. There was another role play question, but this time I had to explain the concept of the limit of a sequence to someone in pre-calculus. I'm pretty good at this, but the phone interviewer wasn't really playing the part herself, so I subconsciously switched from talking to a pre-calc student to someone more mature. Eventually I was asked another brain teaser (expected, question posted below), which I answered correctly and was able to explain in detail. The idea was the same as the jelly bean problem and you solve it the same way. I thought that since the phone interview was kind of awkward and my personality didn't jive with the phone interviewer's, I would get a rejection e-mail immediately. Instead I got instructions for a written assignment (to write solutions to sample math problems at the 3rd grade level & at the high school level, make suggestions for the website, how the problems might vary, what sort of options there should be available for these kinds of problems, etc.) to complete within a week. By this point in time, I didn't really want to work for this company anymore (recently learned that I can't move to CA for personal reasons) and so didn't spend much time on the assignment. I did submit it anyway and heard back less than three days later with the rejection letter--I appreciate their timeliness, and the letter was friendly enough. Not sure what exactly about my application led to them ultimately rejecting me (I am one of the highest rated instructors at my university, not just in math, and have a decent amount of programming experience, so I certainly have the skill set they're looking for). If I had to guess, it would be because I didn't get along well enough with the interviewer, but I guess I don't really care what the reason was.