Not the original cover. No packaging for either TRS-80 title has surfaced; this is a modern illustration made for this archive, after the locations in Betts’s design notebook.
Forbidden Valley
A jungle adventure. The notebook grid opens at a wreckage with a fossil, torch and matches, then works through rocky outcrops, a carnivorous plant, caves of stalagmites and fluorescent pools, a monstrous spider and its web, a native village where the player is tied to a stake, a bubbling mud pool with a hungry dinosaur, and a crumbling stone bridge over boiling lava. The last message in the verb table is line 11000, “Escape — end of adventure”.
Source: Brian Betts's design notebook — the game itself is not known to survive.1981 · No year on any surviving artefact — placed with The Secret of Flagstone Manor, whose title screen reads 1981
No copy of the program is known to survive anywhere. The design notebook and a sheet of unused cassette labels are all that is left.
Design notebook
A page from Brian Betts’s working notebook: the verb table with the BASIC line number each command jumps to, an abbreviation key for the puzzles, and a hand-drawn grid of every location. A sheet of unused printed cassette labels lies across the spread.
A modern Commodore 64 re-creation
This is not a Mountain Valley release. Forbidden Valley was a TRS-80 game, and no copy of it is known to survive — so this is not a port: there is no listing to port. It is a new program in Commodore BASIC, written by Scott Julian in 2026 from the locations, objects, verbs and messages in Betts’s design notebook, to fill the gap until the original is found. It cannot tell you how Betts’s game actually played. Everything above this line is the historical record; this section is not.
Your plane has gone down. You crawl from the wreckage with little more than a lamp and a box of matches, and find yourself somewhere no map dares to name: the Forbidden Valley.
Steaming jungle. Pools of lava. Caves where the darkness itself can kill you. And the creatures that call this place home have no intention of letting you leave.
A crumbling bridge you shouldn’t trust. A serpent coiled in the shadows. An outraged monkey, a hungry dinosaur, a monstrous spider, and a native village whose cooking pot is always on the boil. Every one of them stands between you and freedom. Brute force won’t save you here — only your wits will.
It is built on the notebook: the same eighteen locations, from the wreckage of the plane through the caves, the native village and the mud pool to the rocky gully beyond the spider’s web, and the same 23-command verb table. Where the notebook gives only a location or an abbreviation, the puzzle and the wording around it are new.
Two-word commands — GO NORTH, LIGHT LAMP, FEED DINOSAUR — with HELP if you are stuck. SAVE and LOAD write to the disk in drive 8. Before the title, a screen explains where the game came from and credits the original idea to Betts.
The listing below is the source of the program on the disk: tokenised, the two are the same program.
- Disk image (.d64) 171 KB — the re-creation, for VICE or any C64 emulator
- BASIC listing — the re-creation Commodore BASIC V2, plain text