`Piano` update
-
use single loop for black and white keys -
top_rect -
squares -
#79 (closed) -
#84 (closed) -
#87 (closed) -
add black key to main tests -
#83 (closed) -
#72 (closed) -
#75 (closed) -
#78 (closed) -
#81 (closed) -
#88 (closed) -
#89 (closed)