I finally discovered why I couldn't get the turnLockUp() method to work. I didn't know what the "lock" looked like or where on the platform to find it. It is on the forward edge of the platform. The Expert must be moved to the tile before the lock - which is just some amorphous blob on the screen that doesn't resemble a lock in any way - and then the turnLockUp() method invoked.
Once that's done, nothing dramatic happens. You have to look on the right side of the platform, where the final gem is located. A small, white disk rises slowly up to the main level of the platform. Now it is possible to move the Expert to the tile over which the last gem is positioned.
This was an extremely frustrating experience. The developers of the Swift Playground would do well to review the instructions in this lesson. Maybe indicate what a "lock" looks like and where it is located, perhaps?
Topic:
Developer Tools & Services
SubTopic:
Swift Playground