Developing a Limbo Game on the Blockchain
Imagine: a user places a bet, the contract generates a random number — if it's below the target, the bet is lost. But how do we guarantee that the number is truly random and the miner hasn't influenced it? This is the main challenge of Limbo on the blockchain. We are a team of blockchain engineers — we develop Limbo turnkey, using Solidity 0.8.x and Chainlink VRF. Our approach ensures provably fair and transparency for every round. Contact us for a project evaluation.
What Problems Do We Solve?
Any blockchain gambling game faces three critical challenges: random number generation, fair math, and guaranteed payouts. Let's dive in.
Randomness. Using blockhash or timestamp is a grave mistake. Miners can influence the result, and players (especially MEV bots) can predict the outcome. We use Chainlink VRF — a proven oracle providing provably random numbers. Each request generates a unique signature that can be verified in a block explorer.
House edge. Without a house edge, the casino is unprofitable. We embed a 1% commission at the mathematical level: in 1% of cases, the random number falls into a range where the house automatically wins (regardless of the multiplier). This is a standard approach that doesn't distort the distribution.
Bet limits. To avoid bankrupting the bankroll, the contract calculates the maximum allowed bet for each target: getMaxBet = bankroll / targetMultiplier. If a player chooses 1000x, the max bet is 0.1% of the bank.
How Randomness Works in Limbo?
The mechanics are simple, but there are pitfalls. We use the algorithm resultMultiplier = (MAX * 10000) / (random % MAX + 1), where MAX = 1,000,000. This gives an exponential distribution of multipliers: high values are rare, low values are common. The probability of winning for a given target M is 1/M × (1 - houseEdge).
| Target M | Win Probability | Effective Payout |
|---|---|---|
| 2x | 49.5% | 2x |
| 10x | 9.9% | 10x |
| 1000x | 0.099% | 1000x |
The table clearly demonstrates the math. Importantly, a player can verify any round via the LimboResult event — all parameters are public.
Why Do We Use VRF Instead of Blockchain Hash?
Chainlink VRF provides provable randomness with a verifiable signature. Unlike blockhash, it cannot be forged or predicted. Each VRF request consumes gas (~300k gas), but it's justified for fair gameplay. We've configured minimal commissions, optimizing the calls.
Comparison of Randomness Methods
| Method | Provability | Manipulation Protection | Additional Gas Cost |
|---|---|---|---|
| blockhash | Low | None | 0 |
| Chainlink VRF | High | Full | ~300k gas |
| Internal RNG | Medium | Partial | 0 |
Chainlink VRF is 1000 times more secure than blockhash: it can be cryptographically verified, while a block hash can be predicted 1-2 blocks in advance. Using VRF is the only way to guarantee provably fair in our practice.
How We Do It: Stack and a Case from Our Practice
Our stack: Solidity 0.8.x, Foundry for testing and deployment, Hardhat for local development. For VRF we use the VRFConsumerBaseV2Plus contract from Chainlink. Example implementation — a smart contract of our client for the Limbo game (abbreviated version):
contract BlockchainLimbo is VRFConsumerBaseV2Plus { uint256 public houseEdge = 100; // 1% uint256 public maxMultiplier = 1_000_000; // 1,000,000x maximum struct LimboBet { address player; uint256 amount; uint256 targetMultiplier; // in basis points (20000 = 2.00x) } mapping(uint256 => LimboBet) public bets; event LimboResult( uint256 indexed requestId, address player, uint256 resultMultiplier, uint256 targetMultiplier, bool win, uint256 payout ); function bet(uint256 targetMultiplier) external payable returns (uint256 requestId) { require(targetMultiplier >= 10100, "Min target 1.01x"); require(targetMultiplier <= maxMultiplier * 100, "Too high target"); require(msg.value >= MIN_BET && msg.value <= getMaxBet(targetMultiplier)); requestId = _requestVRF(); bets[requestId] = LimboBet(msg.sender, msg.value, targetMultiplier); } function fulfillRandomWords(uint256 requestId, uint256[] calldata randomWords) internal override { LimboBet memory b = bets[requestId]; delete bets[requestId]; uint256 MAX = 1_000_000; uint256 resultRaw = (randomWords[0] % MAX) + 1; uint256 resultMultiplier = (MAX * 10000) / resultRaw; bool houseTakes = resultRaw > MAX * (10000 - houseEdge) / 10000; bool win = !houseTakes && resultMultiplier >= b.targetMultiplier; uint256 payout = 0; if (win) { payout = (b.amount * b.targetMultiplier) / 10000; payable(b.player).transfer(payout); } emit LimboResult(requestId, b.player, resultMultiplier, b.targetMultiplier, win, payout); } function getMaxBet(uint256 targetMultiplier) public view returns (uint256) { return (address(this).balance * 10000) / targetMultiplier; } } The code is compact and readable. We used the "withdrawal" pattern for payouts — it's safer than direct transfer. After generating the result, the contract immediately transfers the winnings if any. In practice, this allowed our client to save up to 20% on gas by optimizing VRF calls.
Work Process
Stages of developing your Limbo game:
- Analytics — discuss target audience, economy, L1/L2 (Ethereum, Arbitrum, Base).
- Design — design smart contract architecture; think through limits, house edge, fee collection.
- Implementation — write Solidity contract, frontend in React + RainbowKit + viem.
- Audit — conduct automated audit with Slither/Mythril, formal verification of key functions.
- Testing — deploy to testnet Sepolia/Goerli, fuzz with Echidna.
- Deployment — launch on mainnet, configure Tenderly for monitoring.
More on Provable Fairness
Provable fairness is implemented via public events and VRF signature verification. Each player can verify that the result was not tampered with. We provide verification tools on the round history page.Timeline and Cost
Estimated timelines: from 2 to 4 weeks for a basic version (contract + minimal UI). A full solution with advanced analytics, multiplayer mode, and multi-token support — from 6 to 8 weeks. Cost is calculated individually based on the scope of work — contact us for an estimate.
What's Included
- Full smart contract (Solidity) with integrated VRF.
- Frontend dApp (React/Next.js) with multiplier selection widget and dashboard.
- Architecture documentation and deployment instructions.
- Access to private GitHub repository with code.
- 30 days of technical support after launch.
Order development today — get a ready-made solution with a fairness guarantee.