# Bulls & Cows

> ⚠️ **Experimental — generated with no human supervision.** This realm was
> produced automatically by an MCP-driven agent to exercise the gno MCP server
> and tooling, and to generate test content for gno compilers, linters and
> formatters. **Not audited. Not for production.** Full context & folder README:
> [r/moul/x/daily](https://github.com/moul/gno-contracts/blob/main/r/moul/x/daily/README.md)

---


A shared on-chain [Bulls & Cows](https://en.wikipedia.org/wiki/Bulls_and_Cows) puzzle
(the classic ancestor of Mastermind and Wordle-for-digits). One secret 4-digit code
with no repeated digits is live at a time; anyone can call `Guess` with a candidate
code and gets back **bulls** (right digit, right position) and **cows** (right digit,
wrong position). First caller to land 4 bulls cracks the round, lands on the
leaderboard, and a fresh secret is drawn immediately so the next round starts at once.

Realm: `gno.land/r/g12cs4cehujpffpjpywmkqj43m6u5ya53nj69sjz/bullscows`

## Example calls

```
Guess("1972")   -> "1972 -> 1 bulls, 2 cows"
Guess("7192")   -> "*** SOLVED *** 7192 was it — round 3 cracked in 5 guesses. New round 4 has begun, good luck!"
GiveUp()        -> "round 4's code was 4082 — round 5 is live now."
```

`Render("")` shows the current round, attempts so far, the last 10 guesses with
their bulls/cows, and the top-5 fastest-solve leaderboard.

The secret is generated deterministically from the on-chain block height and the
round counter via a small LCG (`newSecret`/`nextRand` in `bullscows.gno`) — no
external randomness needed, and nobody can precompute the next code before its
round actually starts.

## Toolchain status

Verified locally with `gno test -v .` and `gno lint .` against a `gno.land/gnolang/gno`
master checkout used as `GNOROOT` (the default installed `gno` binary had a stale/
missing `GNOROOT`, so `GNOROOT=<path-to-gnolang/gno> gno test .` was used instead).
All 7 tests pass, lint is clean. This exercises current sapphire (gno 0.9) stdlib
paths (`chain/runtime`, no `std` package) and the `cur realm` / `cross(cur)` crossing
convention.

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---

Part of **[moul/gno-contracts](https://github.com/moul/gno-contracts)** — moul's versioned gno.land contracts. See the repository for the full catalog, build/test tooling, and usage.

> 🧪 **Highly experimental — potentially vibe-coded.** Not audited; may break, change, or be removed at any time. Do not use with anything of value. Full disclaimer: [DISCLAIMER](https://github.com/moul/gno-contracts/blob/main/DISCLAIMER.md).

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