start-case

name	start-case
description	Start a new murder mystery game — invent a fresh cast and crime, fairly pick the murderer, and seal the solution so it stays hidden. Use when the user says "start a murder mystery", "new case", "deal a mystery", "let's play detective", "begin the whodunit", or runs /start-case.
allowed-tools	Bash(node:*), Write, Read
context	fork

Start a Murder Mystery (authored live, in a forked context)

You are running in a FORKED context. You will INVENT a fresh mystery, seal the solution to disk, then set the scene by presenting the public briefing. The main game session must never learn the murderer — only the public briefing ever leaves this fork.

0. Make sure Node.js is available (do this FIRST)

sealed-room runs on Node.js. Before generating anything, check it:

node --version

• If it prints a version (v18+ ideally), continue to step 1.
• If node is not found, do NOT generate a case. Tell the player Node.js is required and offer to install it, then install it — only with their go-ahead — using the command that fits their machine:
  • Windows (winget): winget install -e --id OpenJS.NodeJS.LTS
  • macOS (Homebrew): brew install node
  • Debian / Ubuntu: sudo apt-get update && sudo apt-get install -y nodejs
  • Fedora / RHEL: sudo dnf install -y nodejs
  • No package manager / unsure: point them to https://nodejs.org (download the LTS installer).
• After installing, node may not be on PATH until they open a new terminal or restart Claude Code. Ask them to do that, then run start a murder mystery again.

Do not proceed past this step until node --version succeeds.

1. Fair coin-flip — who is guilty

The guilty suspect's number, chosen at random and fairly: !node -e "console.log(require('crypto').randomInt(5)+1)"

Hold on to that number. The suspect you place at that position in step 2 is the murderer.

2. Invent the case

• A victim: name, the room they died in, the time, and an everyday weapon-of-opportunity.
• Exactly 5 suspects, each with a distinct name, role, and voice. The suspect at the coin-flip number above is the murderer.
• Make it solvable (critical):
  • Exactly ONE other suspect is a witness whose truthful account places the murderer near the scene at the time.
  • The murderer has a false alibi that the witness's account contradicts.
  • The remaining suspects each hide an unrelated guilty secret (red herrings) — shifty, but innocent.
• Give each suspect a sheet: identity, demeanour, stated alibi, what they know, what they must conceal/deny, their tell, and how they behave under pressure. Never write "you are the murderer" in a sheet — encode guilt only as what they must deny and how they crack.
• A few clues for examine: the murder room (struggle + the weapon on the floor), body (room/time/weapon), and 1–2 other rooms ("nothing here").

3. Seal it (inline; leaves no plaintext solution behind)

a. Use the Write tool to save the full case as plaintext JSON at .murder-case/_tmp.json, exactly this shape:

{ "victim": "", "location": "", "time": "", "weapon": "", "murderer": "",
  "suspects": [ { "name": "", "role": "" } ],
  "sheets": { "<name>": { "identity": "", "demeanor": "", "alibi_claim": "", "knows": [], "conceal": [], "tell": "", "pressure": "" } },
  "clues": { "<place>": "", "body": "" },
  "briefing": "<PUBLIC markdown: victim + room + time; the 5 suspects, each with their name, role, AND their stated alibi (the one-line `alibi_claim` — where they say they were when the victim died); and a short how-to-play. The stated alibis are public and MUST appear here so the player starts with everyone's story on the record. NEVER reveal the murderer, the weapon-as-proof, who the witness is, or any hidden sheet detail (what a suspect knows, conceals, their tell, or how they crack).>" }

b. Run this inline sealer (it encodes the case, writes the public briefing, and deletes the plaintext):

node -e "const fs=require('fs'),K=Buffer.from('a-mystery-most-foul');const j=JSON.parse(fs.readFileSync('.murder-case/_tmp.json','utf8'));const s=Buffer.from(JSON.stringify(j),'utf8'),o=Buffer.alloc(s.length);for(let i=0;i<s.length;i++)o[i]=s[i]^K[i%K.length];fs.mkdirSync('.murder-case/sealed',{recursive:true});fs.writeFileSync('.murder-case/sealed/case.dat',o.toString('base64'));fs.writeFileSync('.murder-case/briefing.md',j.briefing);fs.unlinkSync('.murder-case/_tmp.json');fs.writeFileSync('.murder-case/actions','0');console.log('SEALED '+j.suspects.length+' suspects')"

4. Set the scene (the opening briefing)

The solution is sealed — now open the game for the player.

Returning detective's record: !node -e "const fs=require('fs');const f='.murder-case/highscores.json';let arr=[];try{arr=JSON.parse(fs.readFileSync(f,'utf8'))}catch(e){}if(!arr.length){console.log('NONE');process.exit(0)}const s=arr.filter(r=>r.result==='solved');const best=s.length?Math.min.apply(null,s.map(r=>r.score)):null;console.log('record :: '+arr.length+' game(s), '+s.length+' solved'+(best!=null?', best score '+best:'')+' :: last case: '+arr[arr.length-1].mystery)"

• If that line is anything other than NONE, open by welcoming the returning detective with their record — games played, how many solved, best score, and their last case — a quick "previously…" before the new mystery. Mention they can run scores for the full leaderboard.
• Then present the public briefing: read .murder-case/briefing.md (PUBLIC — it contains no solution) and set the scene in an atmospheric host voice — the victim, where and when they died, and the suspect line-up. For each suspect, give their name, role, and their stated alibi — every suspect's story belongs on the record from the outset, so the player can start playing the alibis against each other (and against examine findings) instead of having to interrogate everyone just to learn where they each claim to have been.
• Close with what they can do next: interrogate a suspect, examine a place or the body, or accuse when they are ready.

Reveal nothing beyond the public briefing — never the murderer, the weapon-as-proof, who the witness is, or any hidden sheet detail (what a suspect knows, what they conceal, their tell, or how they crack under pressure). The five stated alibis are public and belong in the briefing; the truth that breaks one of them is not. (The high-scores file is public and safe to read; the sealed case is not.)