MIMEcroft.sh

a first-person 3D maze treasure hunt rendered over WebGL — written entirely in bash

opens the shell at www/index.html and auto-starts the game via the allow-listed ?demo=mimecroft.sh parameter (see SECURITY.md) — the game boots as the mimecroft command. You can also just open the shell and type mimecroft.

What it is

You are a lost shell command inside a corrupted filesystem. The maze around you is made of data blocks — coloured chunks of file content. Somewhere in the depths lie hidden treasures: the Great Operating Systems (GNU Hurd, Linux, FreeBSD, NetBSD, OpenBSD, Plan 9, Minix, Solaris, macOS Darwin, Unix) preserved as artifacts. But the filesystem is infested with evil MIMEs — misbehaving content types (image/jpeg, image/png, application/octet-stream, text/plain) that hunt you through the corridors.

Your gun fires a single ray of pure type-checking. Shooting a block mines through the data; shooting a MIME sanitises it. Walk into a hidden treasure to recover it — shooting one shatters the artifact and costs you an archaeology-licence strike (three strikes and the Board revokes it).

WASD move · ←/→ turn · SPACE shoot · Q quit · ESC settings

The settings menu tweaks the camera shift, texture size/seed, CRT & corruption effects, the minimap, mime speed and the sound mode (notes oscillators or bash — sample-accurate generators).

Why it's interesting

The whole game is one bash script (bin/mimecroft.sh, ~3,900 lines) that runs in the browser via the shell's bash→JS transpiler — no build step, no WebGL API calls in the game itself.
The GPU shaders are written in bash too and compiled to GLSL ES 1.00 at startup by the sh→GLSL backend (see WRITING_GPU_SHADERS_IN_BASH.md).
The block textures and sound effects are synthesised by bash: pseudorandom value-noise texture generators and sample-accurate DSP sound generators, all deterministic per seed.
Every browser capability is a file: the game renders by writing cubes to /dev/webgl and plays by writing samples to /dev/audio — the Plan 9-style filesystem-as-API metaphor (see bash-game-vision.md and mimecroft-proposal.md).

The implementation — the .sh files

bin/mimecroft.sh ~3,900 lines

The game itself — the mimecroft command. One script does everything:

world generation — a seeded drunkard's walk carves the corridors over a 16×16×3 block grid; an indestructible obsidian ring borders the maze; coloured gem blocks and grass patches are scattered deterministically
rendering — a painter's-algorithm scan (far-to-near along the facing axis) writes every visible cube to /dev/webgl/blocks in one batched payload per frame; a continuous frustum culls off-screen cells; floor/ceiling planes follow the camera
gameplay — movement/turn glides, a ray-cast shot with per-material hardness and damage (blocks crack, then break), hidden treasures claimed by walking in, and MIME entities that hunt or flee
HUD — a canvas radar/minimap, score/hp/licence/fps digits in a 3×5 pixel font, floating treasure-name labels, a view-model gun with muzzle flash, and the settings menu
assets — loads the generated textures, treasure labels and MIME banners through /dev/webgl/texture, and plays sounds through /dev/audio

examples/mimecroft-vertex.sh ~50 lines

The vertex shader authored in bash. Object→world transform, the camera-relative delta, the yaw rotation (cos/sin via bc), and the fake perspective (gl_Position = (rel×0.45, w²/64, w)). Compiled at startup by sh2glsl --vertex into GLSL ES 1.00; the compiled reference is examples/mimecroft-vertex.glsl.

examples/mimecroft-frag.sh ~68 lines

The fragment shader authored in bash: per-pixel block-texture tint, the crack-overlay blend on damaged blocks, and the optional CRT scanlines / corruption streaks / vignette. Every intermediate is bounded to fit precision mediump int. Compiled by sh2glsl; the compiled reference is examples/mimecroft-frag.glsl.

examples/textures/ 17 generators

Pseudorandom, seamlessly tileable block textures, generated by bash (seeded LCG + value noise, no floats, no $RANDOM), deterministic per seed. README. The core texture-lib.sh is inlined into each generator so they run identically under host bash, the real-bash wasm, and the transpiled shell:

stone · sandstone · dirt · grass · leaves · wood · brick · water · obsidian — the block walls/floor
chest — the treasure-artifact side (wood + iron struts + latch)
crack — the transparent RGBA damage overlay on mined blocks
jpeg · png · octet · text — the MIME entity icons (a tiny DCT-grid photo, a transparency checkerboard, a hex dump, a text page)
read-texture.sh · make-textures.sh — TSV reader + one-shot PPM→PNG→contact-sheet batch

examples/sounds/ 12 synthesizers

Every game sound as a list of signed 16-bit PCM samples at 22050 Hz, synthesised in bash (sine-table waveforms, envelopes, seeded noise) and played through /dev/audio/samples in the game's bash sound mode. README:

hit (material-dependent tick) · break · thud · shoot · kill · damage
treasure (recovery fanfare) · shatter · walk · mime
make-sounds.sh (batch .wav/.tsv) · audition-sounds.sh (A/B audition)

How it runs

The page's bash→JS transpiler turns mimecroft.sh into JavaScript against the sh2 runtime; the /dev/webgl device (src/fs/webgldev.js) provides the WebGL context as files (shader/, buffer/, uniform/, call, blocks), and /dev/audio plays the notes or sample lists. The same script runs headless in the Node CLI (a null WebGL device), which is how the game is regression-tested.

MIMEcroft lives in the j.cmd repo — the game, its shaders, textures and sounds, all written in bash.