Come to think of it, it would be nice if we didn't even need to specify the `ac` at all. On our computers it should use PygletAudio and keyboard automatically, whereas on the lab computer it would use `TDT` and buttonbox automatically. Then these lines could then just be eliminated altogether, which is a nice simplification. I don't think most users will care about these options so long as we have them set up correctly on each machine, and it would simplify the example not to have to do it. WDYT?