I love to occasionally just recreationally read over the OpenFirmware source code as fine literature, especially the kernel and metacompiler, since it's just such elegant beautifully polished and refined code, the results of so many decades of meticulous work on so many platforms and devices.
Forth is really a transparent "glass box" where you can see through and understand it all from top to bottom, and OpenFirmware includes a museum of drivers and modules and extensions for everywhere it's ever been and all of its missions, like Superman's Crystal Fortress of Solitude!
>The Fortress contained an alien zoo, a giant steel diary in which Superman wrote his memoirs (using either his invulnerable finger, twin hand touch pads that record thoughts instantly, or heat vision to engrave entries into its pages), a chess-playing robot, specialized exercise equipment, a laboratory where Superman worked on various projects such as developing defenses to kryptonite, a room-sized computer, communications equipment, and rooms dedicated to all of his friends, including one for Clark Kent to fool visitors. As the stories continued, it was revealed that the Fortress was where Superman's robot duplicates were stored. It also contained the Phantom Zone projector, various pieces of alien technology he had acquired on visits to other worlds, and, much like the Batcave, trophies of his past adventures. Indeed, the Batcave and Batman himself made an appearance in the first Fortress story. The Fortress also became the home of the bottle city of Kandor (until it was enlarged), and an apartment in the Fortress was set aside for Supergirl.