Don't initialize the ButtonChooser with lowercase letters

Otherwise, you could get an inscrutable ValueError, 'Key already bound' error message. Always use uppercase letters, and all should be well. I think this has something to do with the error-checking in the KeyboardTrack that won't allow multiple ButtonChoosers to simultaneously be checking the same key.

I can't quit from the experiment!

Make sure you have exp.setBreak() in your code. Then you should be able to use Esc-F1

N.B. on the Mac, the F1 key doubles up as a brightness control, and so you have to hold down the 'Function' key to get it to behave, so you'd hold down Fn, and then press Esc-F1.

None of my keypresses are taking effect!

Make sure you set up a KeyboardTrack.