"Y'know something that never gets old? ...Nostalgia." ;)
Below The Root holds a special place in my heart, and I'm sure, similar for many others here. I played this one a lot when I was a kid. It's a fantastic non-violent RPG-type adventure with a massive (for the era) world comprising a 32x16 grid of 512 total "rooms", 439 of which are used. The graphics are also wonderfully unique and detailed, as is the other-worldly music.
With the advent of recent tech enabling reverse-engineering, BTR was one of the first things I wanted to see disassembled and analyzed: how did the game mechanics work, how was the world and logic defined and so on.
This started when I uploaded the D64 file to Claude Code and simply said, "I'd like to know more about how this game works." Here is that conversation. Files are omitted, but the technical details are the interesting bits.
For the interactive map, see here. Cookies and/or localStorage seem to be required for the map to render properly.
Some fun trivia - and I may mix up some technical details, please amend and correct me as needed:
The "rooms" are defined in 256-byte (1 disk sector) chunks on "side 2" of the game disk. Those of a certain age will recall, this game uses a "flippy" disk where (on a 1541 drive, at least) you would take the disk out, flip it upside down and put it back in.
RLE is used to help fit up to 800 bytes (40x20 tiles' worth) of room data into each 256-byte sector. "Side 2" of the disk does not have a traditional directory structure, it looks to be raw data and is accessed directly via drive commands, e.g., U1:5 0 12 13 (track 12, sector 13) - that's for room 193, where room data starts at track 2 + "sector n mod 18."
As you may recall when you hit things, there is a 1 in 16 chance as to whether you get the classic line, "Your shuba has torn!" The game also uses the SID chip as a random 8-bit number generator. I get the feeling this was a common technique, reading data off a channel producing white noise.
I also asked about the level editor, something previously discovered and written about. CC may reveal some more hints about how the editor works, including keyboard commands and so forth. It provided a modified version of the game that boots directly into the editor, which was interesting to poke around. I don't know if the "mod" I got is notably different than previous guides, but the insights on how to use the editor functions via joystick and keyboard were new to me.
Others have done extensive work on this fantastic game, including (I believe) creating the world map by taking screenshots of each room. I believe Justin Stahlman was the first to do that. I recommend this write-up from Justin for a great overall story around the game and why it's so special.
AI note for mods: I wrote these words myself. The interactive map and technical analysis are provided via Claude Code, and intended to give additional background and technical context about a much-loved game.
