Mines

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How it keeps the board secret

• The board is an elist of ebool, length N squared. One entry per tile, true means bomb.
• Bombs are placed with a single shuffle. That gives a uniform distribution in one Inco op, with no per-bomb bias.
• Each click is O(1). e.getEbool(board, pos) reads one cell instead of scanning every bomb.
• A sticky encrypted accumulator tracks the whole game. ebool everHitBomb is updated with e.or on every pick, so cashout verifies exactly one attestation no matter how many tiles the player opened.

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The flow

createMinesContract   deploy a game, shuffle the board (one Inco fee), reserve max payout
pickTile(pos)         ebool hit = e.getEbool(board, pos); e.reveal(hit)
                      everHitBomb = e.or(everHitBomb, hit); e.reveal(everHitBomb)
frontend              attestedReveal([hit, accumulator]) with no wallet signature
cashOut(sig)          contract verifies the covalidator signature, requires no bomb was hit

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Contracts

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Running it

git clone https://github.com/Inco-fhevm/mines.git

# contracts (pnpm)
cd contract && pnpm install
pnpm hardhat test test/Mines.multiplier.test.ts   # pure math, no chain
pnpm hardhat run scripts/deployForFrontend.ts --network baseSepolia

# local Inco node instead of testnet
pnpm node:up      # anvil (8545) + covalidator (50055)
pnpm test:anvil
pnpm node:down

# frontend (npm)
cd ../interface && npm install && npm run dev

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Honest limitations

• The factory must hold enough ETH to cover the max payout of every active game. Mines multipliers explode at higher mine counts, so a 5 by 5 board with 5 mines needs about 53 ETH in reserves per 0.001 ETH bet. Boards with 7 or more mines are effectively unusable on testnet.
• After the timeout fix, expireGame refunds the bet on timeout. That is correct for a winning player who could not cash out in time, but it also refunds a player who hit a bomb and walked away. A real product would require an attestation proving no bomb was hit before refunding.