Thank you, Keppel. This is a pretty basic project compared to that. I think Transparent takes out the World: Sky background. Here's the current tutorial I'm working with (Magic Mineral): https://www.youtube.com/watch?v=KpWWYEF59lo The part I'm stuck on begins at about 46:40. It's one of the best tutorials I've seen, showing each step and even explaining why he's doing it. I've learned more about how the nodes work from this than any other.

Here's another with the same problem (Simple Energy Effect): https://www.youtube.com/watch?v=bnrsoSagIU8 Trouble at 9:30.

Since both projects are having the same problem, I'm guessing there's just a detail I'm missing that was too obvious for them to mention. They both use older versions of Blender, 2.66.1 and 2.7. Comments mentioned some node issues with newer versions. Thank you for your help!