Zuno

Zero-knowledge UNO on Stellar.

A trustless multiplayer UNO game where your hand stays private. The blockchain only ever sees cryptographic commitments and proofs — never your cards. Moves are verified onchain, the pot is settled by the contract, and there is no host or server in the loop.

How it works

• Each player commits to a hash of their hand onchain. Actual cards live only on the player's device.
• A Noir circuit proves a move is legal: the card was in the hand, and it matches the top of the discard pile. The contract verifies the proof, updates state, and advances the turn.
• When a hand hits zero, the pot is settled onchain. No arbiter, no off-chain trust.

Stack

Layer	Tech
Chain	Stellar (Soroban, Protocol 22)
Contracts	Rust + soroban-sdk 22.0.0
ZK circuits	Noir (nargo 0.36)
Prover (web)	noir_js + bb.js
Wallet	Freighter
Frontend	Next.js 16 + Tailwind

Deployed contract (Stellar Testnet): CBZVYOLXMVQYGHTJDRVRSB7ABR74UDV7CUIIMMHEH2JAEYAKQJOMJNAW

Features

• Private hands — Mental-poker-style commitments; cards never touch the chain.
• ZK-verified moves — play_card and draw_card ship with Noir proofs, verified onchain.
• Trustless settlement — XLM pot is locked by the contract and released when a hand reaches zero.
• Host migration — If the host leaves the lobby, ownership passes to the next seated player so funds never get stuck.
• AFK protection — Anyone at the table can force-skip after the turn timer expires.
• Zuno call-out — Players with one card who forget to call Zuno get a 2-card penalty.

Repo layout

contracts/                                Cargo workspace
  programs/zuno/src/                      Soroban contract (10 entry points)
circuits/
  play_card/src/main.nr                   Legality + state transition
  draw_card/src/main.nr                   Draw-from-commitment
components/zuno/                          Next.js UI
hooks/                                    Freighter + contract hooks
lib/stellar.ts                            Soroban RPC + Horizon helpers

Run it

npm install
npm run dev

Open http://localhost:3000. You'll need the Freighter browser extension set to Testnet.

Optional override for the deployed contract:

# .env.local
NEXT_PUBLIC_ZUNO_CONTRACT_ID=CBZVYOLXMVQYGHTJDRVRSB7ABR74UDV7CUIIMMHEH2JAEYAKQJOMJNAW

Build

# Contracts
cd contracts && cargo build --release --target wasm32-unknown-unknown --package zuno && cargo test

# Frontend
cd .. && npm run build

---

Built with Noir + Soroban.