Rock Paper Scissors

This repository is a Rock Paper Scissors demo built to show one core idea:

• the same game action is vulnerable when sent through the public mempool
• the same game action is protected when sent through Neo X protected transactions

Game objective

For each round, the contract publishes the house move. The player must submit the correct counter move before the deadline:

• Rock -> play Paper
• Paper -> play Scissors
• Scissors -> play Rock

The first valid winning transaction gets the prize.

How the game works

1. Player starts a round by calling startRound() with a stake.
2. Contract creates round state: player, house move, winning move, deadline, and prize.
3. Player submits playRound(roundId, move) using either:
   • a normal public transaction, or
   • a protected transaction path
4. If the move is correct and arrives first, the caller wins.
5. If the round expires without a winner, refundExpiredRound(roundId) returns funds according to contract rules.

How this showcases anti-MEV

The contract call is identical in both modes. Only the transaction path changes.

• Public mode:
  • playRound(roundId, move) appears in mempool calldata.
  • A bot can read the move and copy the same call with a higher fee.
  • The bot can win by being included first.
• Protected mode:
  • The move is not exposed to public mempool observers before inclusion.
  • The copy-trading bot cannot decode and replay in time.
  • The original player keeps the advantage.

This makes the anti-MEV behavior easy to inspect because game rules stay constant while transaction visibility changes.

Code walkthrough

• contracts/RockPaperScissors.sol
  • core round lifecycle: startRound, playRound, refundExpiredRound
  • validation and payout logic
• bot/frontRunner.js
  • listens to pending public transactions
  • decodes playRound(roundId, move) calldata
  • sends a competing replacement/copy transaction
• frontend/pages/index.tsx
  • UI flow to start a round and submit the winning move
  • side-by-side actions for public vs protected submission
• frontend/lib/envelope.ts
  • protected transaction sending path (Neo X envelope flow)

Local development

Install dependencies:

npm install
cd frontend && npm install && cd ..

Run tests:

npm test

Run local chain:

npm run node

Deploy contract:

npm run deploy:local

Start bot:

npm run bot

Start frontend:

npm run frontend

Environment

Set these in .env:

• NEOX_RPC_URL
• NEOX_WSS_URL
• PRIVATE_KEY
• CONTRACT_ADDRESS
• NEXT_PUBLIC_CONTRACT_ADDRESS
• NEXT_PUBLIC_WALLETCONNECT_PROJECT_ID
• BOT_RECYCLE_WINNINGS (optional, default true)
• BOT_GAS_RESERVE_GAS (optional, default 0.05)