Gym pieces

The pieces the gyms are built from.

Gym Run	Lists a gym's sections and what to try in each.
Gym Challenge	Says what a gym piece asks and how hard it is.
Gym Checkpoint	Where a gym brings the character back.
Gym Door	A door that slides open when called.
Gym Pickup	The goal at the end of a gym.
Platform Mover	Moves a platform back and forth, or turns it.
Collapsing Platform	Drops a floor a moment after it is stood on.
Character Overlay	Shows the state, input and jump arc while playing.