What I loved was when I signed up some time ago they had given me a partial derivative with a single variable, telling me what the variable was. Meaning that the answer was 0. Some of them look REALLY complex but they're actually far simpler than they appear, except for the fact that it'd be incredibly difficult to break them in practice given the variation they produce.

The answer seems to be zero nearly all the time.

I've occasionally seen it where it's -1 or 1. I think it's all three until you measure it.

Nice schrodinger cat reference