Laugh School™ Computers — Fabric 1.21.11 + Geyser (and a Paper build)

Fully working in-game computers for the Laugh School™ Minecraft Server. Not decoys: every command executes real logic, files persist in world NBT, fetch performs real HTTP requests, and both arcade games are genuinely playable.

Two builds come out of this repo:

Build	Artifact	For
Fabric mod (the main event)	laughschool-computers-<version>.jar	Fabric 1.21.11 server + Java clients. Terminal screen, arcade, LaughBrowser, Geyser chat mode.
Paper plugin	laughschool-computers-paper-<version>.jar	Paper 1.21.11 servers that can't ask players to install anything. Shell-only, in chat, for everyone. See §8.

1. Who gets what

Player	Experience
Java + this mod installed	Full CRT terminal screen, Snake & Pong, everything.
Bedrock via Geyser (no mods possible)	Automatic chat mode: right-clicking the computer boots it in chat, commands run via /pc <command>. Full shell, files, and internet — only the arcade screen is Java-mod-exclusive.
Anyone on the Paper build	Chat mode, always — Paper has no client mod to talk to.

The switch is automatic: the server checks whether the client registered the mod's packet channels (ServerPlayNetworking.canSend) and falls back to chat mode if not. All logic (shell, file storage, HTTP whitelist, high-score validation) runs server-side, so both paths hit the exact same brain.

2. Features

• Computer block — Redstone Blocks creative tab, or /give @s lscomputers:computer. Right-click to boot.
• LaughOS shell — help, motd, name, files/write/read/rm (32 files × 512 chars, saved in world NBT), ping, time, uptime, whoami, neofetch, sudo, credits.
• Python — python <expr> runs a snippet in a tiny built-in Python 3 interpreter (variables, arithmetic, strings, comparisons, print/len/str/int/float/abs/round/type/min/max/sum). Statements split on ;, so you can save and run scripts: write hi.py x=21; print(x*2) then python hi.py. No loops/imports/IO — it always terminates and can't touch the game, disk, or network.
• Locking — lock <password> claims the machine and locks it (salted SHA-256, stored in world NBT). unlock <password> logs you in; passwd [new] (owner) changes/removes it; logout re-locks. A reboot re-locks everyone — it's a login prompt, not a keep-out sign. Scores and the browser are gated behind the lock too.
• Internet — fetch example.com: real async HTTP GET, domain-whitelisted, size/time capped, redirects refused, IP literals blocked. Server-side only; unbypassable from clients.
• Web browser — browse [url] opens the LaughBrowser: a text-mode ("Lynx-style") browser with an address bar, arrow-through links, history (Backspace), and page scrolling. Fetching is the same whitelisted, server-side path as fetch. In chat mode browse falls back to fetch.
• Games (Java modded clients) — games, then snake, pong, tetris, 2048, breakout. High scores validated & stored per computer.
• Config — config/laughschool-computers.json, live-reload via /lscomputers reload (op 2). Also editable in-game: run settings in the terminal, or open it from Mod Menu if installed. In singleplayer / a self-hosted world the changes apply immediately. If Mod Menu isn't installed, the settings screen offers a one-click optional download of the matching build into your mods/ folder (takes effect after a restart).
• Easter eggs — try laugh. Old-school gamers should try a certain 10-key code in the terminal.

3. Building

Requires JDK 21+ (25 works fine — the mod targets 21). The complete Gradle wrapper is included (gradlew, gradlew.bat, gradle/wrapper/gradle-wrapper.jar, official Gradle 9.4.0) — no Gradle installation needed:

./gradlew build
# → build/libs/laughschool-computers-<version>.jar          (Fabric mod)
# → paper/build/libs/laughschool-computers-paper-<version>.jar   (Paper plugin)

One build produces both; ./gradlew :paper:build builds only the plugin (much faster — no Minecraft decompile or remap). CI does the same on every push and pull request (.github/workflows/build.yml), and pushing a v* tag builds both and publishes a GitHub Release with the jars attached (.github/workflows/release.yml).

On the first run the wrapper automatically downloads the Gradle 9.4.0 distribution and Gradle resolves the build dependencies (Minecraft 1.21.11, Mojang mappings, Loom, Fabric Loader, Fabric API) from Mojang's and Fabric's servers into your local cache (~/.gradle). That's by design — those artifacts are machine-cached, not project files. After the first build, everything is offline-cached.

The one runtime file to download separately: Fabric API 0.141.4+1.21.11 for the mods/ folders (server + Java clients), from https://modrinth.com/mod/fabric-api/versions (pick the 1.21.11 build).

Toolchain: Minecraft 1.21.11 (the last obfuscated version), Loom 1.14 (net.fabricmc.fabric-loom-remap), Mojang official mappings, Fabric Loader 0.18.1, Fabric API 0.141.4+1.21.11.

4. Server setup (with Geyser)

1. Fabric 1.21.11 server, Java 21+. Into mods/: this jar + Fabric API.
2. Install Geyser-Fabric and Floodgate (both from https://geysermc.org/download) into mods/ as usual.
3. Java players who want the full terminal also install this jar + Fabric API client-side.
4. Bedrock players just join through Geyser — nothing to install, chat mode kicks in.

Honest limitations with Geyser:

• The computer is a modded block, so Bedrock clients render it as a fallback block (Geyser substitutes unknown blocks). It's still fully right-clickable and functional. If you want it to look right on Bedrock, Geyser's experimental custom block mappings + a Bedrock resource pack can skin it — see the GeyserMC wiki ("Custom Blocks"); that's config on the Geyser side, not part of this jar.
• The arcade (Snake/Pong) is rendered by the Java client mod and can't exist on Bedrock. Chat mode says so politely.
• Vanilla Java clients (no mod) still can't join: Fabric registry sync requires Java clients to know the mod's block/item. That's a Fabric/registry fact of life, not something this mod can waive — Bedrock players are exempt because Geyser translates for them.

5. Configuration (config/laughschool-computers.json)

{
  "enableInternet": true,
  "allowedDomains": ["example.com", "api.github.com", "wttr.in"],
  "allowAllDomains": false,
  "maxResponseLines": 16,
  "maxResponseBytes": 8192,
  "requestTimeoutSeconds": 5,
  "motd": "Welcome to LaughOS(TM) ...",
  "easterEggs": true
}

Created with defaults on first run, rewritten on load so new options appear after updates. Only root domains you list are allowed (plus their subdomains) — unless you set allowAllDomains: true, which removes the whitelist entirely and lets fetch/browse reach any host (IP literals and localhost are still refused). You can flip this from the in-game settings screen too.

6. Security notes

• Shell + HTTP run server-side; a hacked client can only send command strings.
• Packets rejected unless the player is within 8 blocks of a real computer (/pc requires ~4 blocks).
• Scores clamped server-side; inputs length-capped and control-character-stripped.
• fetch never follows redirects and refuses IP literals/localhost.

7. Credits

Built exclusively for the Laugh School™ Minecraft Server. No decoys were used in the making of this mod. Bedrock friends welcome.

8. Paper build

paper/ is the same computers as a Paper 1.21.11 plugin, for servers that can't require a mod on the client. It is the mod's server half: the LaughOS shell, the file system, the salted password lock, the built-in Python and whitelisted fetch — the python interpreter is literally the same source file, compiled into both jars.

./gradlew :paper:build
# → paper/build/libs/laughschool-computers-paper-<version>.jar

Drop it in plugins/, restart, then:

1. /lscomputers give — hands you a Laugh School™ Computer (a tagged Lodestone by default; change computerBlock in config.yml to any block you like).
2. Place it, right-click to boot.
3. /pc help, /pc write notes.txt hello, /pc python 2 ** 10, /pc lock hunter2, …

Commands and permissions:

Command	Permission	What
/pc <command>	lscomputers.use (default: everyone)	The terminal. Works on the nearest computer within ~4 blocks.
/lscomputers reload	lscomputers.admin (default: op)	Re-read config.yml; also re-locks every machine and drops registrations whose block is gone.
/lscomputers give [player]	lscomputers.admin	Hand out a computer.
/lscomputers list	lscomputers.admin	How many computers exist, and the nearest one.

What differs from the Fabric mod, honestly

• No terminal screen, no arcade, no LaughBrowser. Those are client-mod rendering. games/browse/settings say so; browse <url> degrades to fetch.
• The computer is a vanilla block wearing a tag, because Bukkit can't register a new block. Placement is tracked by the plugin, so a computer placed from a /lscomputers give item is a computer and a plain Lodestone next to it is not.
• State lives in plugins/LaughSchoolComputers/computers.yml, not world NBT (saved on change every 5 minutes and on shutdown). Breaking a computer drops the item and deletes its files — same as destroying the modded block's block entity. Explosions leave computers standing, and pistons refuse to push them, so a machine can't lose its disk to a stray creeper.
• config.yml uses the same option names as the mod's JSON, plus computerBlock.
• Bedrock players via Geyser get exactly what Java players get here: chat mode. On this build the fallback isn't a fallback, it's the whole product.

computer-mod

computer-mod