There are currently three piano keyboard shortcuts in Playground:
1. PLAY A LESSON: play the highest and lowest keys of your keyboard simultaneously and it will start the segment you're on.
2. REPLAY A LESSON: after playing through a segment, play any "C" key on the keyboard and it will play that segment again.
3. MOVE TO THE NEXT LESSON: after playing through a segment, play any "D" key on the keyboard to move to the next segment.