Rename Main -> Wheel and make Main/Vert subclasses
Add touch detection inside Main's color wheel
Transition to Vert when the wheel is tapped
Vert: use dark background
Vert: use white music ball instead of black
Vert: invert the slice colors
Vert: reverse the order of notes played
Vert: transition back to Main on inner circle tap

This is temporary; I'm planning on replacing it with a back arrow in the
upper left corner of the screen.
Rename vibraphone files to exclude the octave

I was originally thinking the notes would go up/down an octave based on
the number of revolution the music ball makes around the Main scene's
wheel.
Add transposed versions of Main's vibraphone notes

They're transposed down a tritone, otherwise known as exactly half an
octave, to be used in Vert.
Vert: add back button
Provide visual feedback on the back button
Vert: use impulses instead of gravity as controls
Vert: make the slices and music ball bouncy
Vert: create a pentagon from the bars
Vert: add bar thickness
Vert: remove print statements
Vert: use damping instead of friction/restitution
Merge branch 'vert'