In SpaceRL, I added barricaded doors that can only be opened from one side. With these, the level generator can control the order in which the player encounters rooms in the spaceship, while allowing the player to subsequently take shortcuts across the level.
I also added a slight refinement to the way the level generator places doors. It first creates the ship's original door layout, then replaces some of those doors with barricaded or broken doors to restrict the player's travel path. Previously it was only doing one pass to establish the connectivity of the ship's rooms. With this algorithm there is a slight bit of history implied in the level, as you can see the ship's original symmetric, non-maze door layout underneath the current restricted connectivity.
I logged into Facebook (as I do every other month or so) and discovered that Chad Jones, an artist with whom I worked on two games over the course of four years, has written an e-book about his last decade-plus of experience working in the games industry. It's a dollar and a good read, especially for anyone thinking about going into games. It's available for Kindle and Nook. The book's called “Laid Off” which in boxed games development is the usual disincentive for shipping a product.