This is it exactly. It opens up the door to even more complexity in the design... Now that you can unselect floors, if the elevator is on its way to the 5th fl

This is it exactly. It opens up the door to even more complexity in the design... Now that you can unselect floors, if the elevator is on its way to the 5th floor and you unselect it, should it skip that floor mid-movement? If there's only one floor selected, we'll probably want to disallow unselecting it while the elevator is moving, but what if you just hopped on and it hasn't moved yet? This would probably make for an interesting interview question.