I think the thing to remember is that gadgets are not meant to be full-fledged apps. They are meant to provide a view into data or other apps in a
limited way. So, while the comments by the interviewer about writing a Quake III gadget may be possible, it would be contraindicated in this context.
I agree with a previous post...although the interviewer had some insightful questions, his constant joking was distracting.