Remove unison intervals.
Add a function for checking if NoteContainers match, disregarding octaves, and unit tests.
Change isNoteOn/Off to use underscores.
Move Beastie logic into the superclass and make distinct subclasses.
Check that any notes were heard in heard_count.
Return whether notes were right or not if handleNote has heard enough.
Allow animation steps not to trigger sounds.
Add finish method to clean up after an attack is completed.
Rename creature_widgets to beastie_widgets. Better on_deck handling. Keyboard annotations.

Make a method to get the next on_deck creature so that better logic
than “pick a random one” can go there later. Use some more
sophisticated mechanisms to allow more keyboard key annotations.
Add a comment with instrument names for reference.
Use switch_to for screen switching. Store screens in a dict.