Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Funny. Challenging. Moving.

Get ready for some surprises with this one. When I began watching this documentary about the lives of four men and the work to which each devotes his life, I laughed a lot. They were funny to me, these odd people and their singular obsessions. I laughed, then I started feeling a little guilty, voyeuristic, laughing at them while they were so naked about the things that moved them. And I felt a little angry with Errol Morris for exploiting them. Then slowly Morris starts overlapping one man's story with another's video, and I realize that he IS in control, his sincerety intact. Far from making mockeries of these men, he takes their disparate interests and views and makes a profound statement about life and what is at the center of it. Very funny. Very challenging. Very moving. And I fell in love with the robot maker.