Building Game Experiences with The Sandbox SDK
A player enters an exclusive content zone, but the game doesn't check whether they own LAND — immediate user disappointment. Integrating The Sandbox SDK solves this in a few lines of code. Instead of writing custom Solidity smart contracts, setting up Polygon interaction, and creating a separate marketplace, you use ready-made SDK tools. This reduces development costs by up to 70% and cuts timelines from months to weeks. We do this turnkey, saving your time.
Custom development of the same features without the SDK would take 2–6 months and require a full security audit. The Sandbox's audited contracts cover 90% of typical scenarios: LAND ownership check, ASSET purchase, content gating. On average, SDK-based integration speeds up time to market by 3x — from half a year to two weeks for basic functionality.
With over 10 years in production and 40+ successful projects, we bring proven expertise to every integration.
What Problems Does The Sandbox SDK Solve?
SDK includes VoxEdit for voxel assets, Game Maker for visual scripting, and TypeScript SDK for custom logic. Additionally, REST API for the marketplace and GraphQL for LAND data are available. Key problems we solve with the SDK:
- Real-time LAND ownership verification. We use
ethers.jsto call Polygon contracts and getbalanceOf. This is the foundation for gating — only NFT owners get access to exclusive zones. - In-game marketplace integration. Via Marketplace API and Exchange contract, users can buy and sell ASSET without leaving the game world. Transaction signing via MetaMask is set up in days.
- Custom game logic in TypeScript. Zone entry, NPC interaction, purchase handling — all written in a familiar stack without diving into Solidity.
Common mistakes in self-integration: wrong ABI, incorrect contract addresses (e.g., LAND address on Polygon), ignoring gas limits in batch calls, missing event handling for state updates. We avoid these issues through experience and using verified libraries.
Step-by-Step Integration Process
- Requirement analysis and game scenarios: defining mechanics — ownership check, asset purchase, gating, NPC interaction.
- Web3 provider setup: connect Polygon via
ethers.JsonRpcProviderorviem, install SDKnpm install @sandbox/game-sdk. - Asset verification logic: use Sandbox Game SDK to get player wallet and call
balanceOfon LAND and ASSET contracts. - Marketplace API integration: configure listing and buying of ASSET via Exchange contract with transaction signing through
window.ethereum. - Testing and debugging: use Tenderly for transaction simulation, Slither for static analysis. Check error handling (insufficient gas, transaction cancellation).
- Deployment and documentation: publish the game experience on The Sandbox map, deliver maintenance docs to your team.
Comparison: SDK vs Custom Development
| Aspect | Without SDK | With The Sandbox SDK |
|---|---|---|
| Required stack | Solidity, Hardhat, ethers.js | TypeScript, Game Maker, VoxEdit |
| Time to MVP | 3–6 months | 2–5 weeks |
| Security audit | mandatory | not required |
| Flexibility | high | medium (covers 90% of scenarios) |
| Cost | high (audit + development) | savings up to 70% |
SDK accelerates development by 3x and reduces error risk — contracts are already audited. If you need maximum customization, we combine SDK with custom contracts.
Code Example: Checking LAND Ownership
TypeScript code with ethers.js
import { ethers } from 'ethers'; // ABI for Sandbox core contracts const LAND_ABI = [ 'function ownerOf(uint256 tokenId) view returns (address)', 'function tokenOfOwnerByIndex(address owner, uint256 index) view returns (uint256)', 'function balanceOf(address owner) view returns (uint256)', ]; const ASSET_ABI = [ 'function balanceOf(address account, uint256 id) view returns (uint256)', 'function balanceOfBatch(address[] accounts, uint256[] ids) view returns (uint256[])', ]; // Polygon Mainnet addresses const LAND_CONTRACT = '0x50f5474724e0Ee42D9a4e711ccFB275809Fd6d4A'; const ASSET_CONTRACT = '0xa342f5D851E866E18ff98F351f2c6637f4478dB5'; async function getUserSandboxAssets(userAddress: string) { const provider = new ethers.JsonRpcProvider('https://polygon-rpc.com'); const landContract = new ethers.Contract(LAND_CONTRACT, LAND_ABI, provider); const assetContract = new ethers.Contract(ASSET_CONTRACT, ASSET_ABI, provider); // Get number of LAND tokens const landBalance = await landContract.balanceOf(userAddress); // Get all LAND tokenIds const landIds: bigint[] = []; for (let i = 0; i < Number(landBalance); i++) { const tokenId = await landContract.tokenOfOwnerByIndex(userAddress, i); landIds.push(tokenId); } return { landIds, landCount: Number(landBalance) }; } This code is the basis for content gating. LAND on the Sandbox map has coordinates (x, y) in a 408×408 grid. Through The Graph you can fetch data:
query GetLandDetails($tokenId: String!) { land(id: $tokenId) { id x y owner { address } estate { id } tokenURI } } Marketplace API Integration
Asset trading is a key metaverse feature. Through the API you can list your NFTs, get price data, and buy directly. Listing requires a MetaMask transaction signature and Exchange contract call.
const SANDBOX_API = 'https://api.sandbox.game'; async function getMarketplaceListing(assetId: string) { const response = await fetch(`${SANDBOX_API}/v1/assets/${assetId}`); return response.json(); } async function getUserCreations(walletAddress: string) { const response = await fetch( `${SANDBOX_API}/v1/assets?creator=${walletAddress}&status=published` ); return response.json(); } // List your own ASSET on the marketplace async function listAssetForSale(assetId: string, priceInSand: string) { const provider = new ethers.BrowserProvider(window.ethereum); const signer = await provider.getSigner(); const sandContract = new ethers.Contract(SAND_TOKEN, ERC20_ABI, signer); await sandContract.approve(MARKETPLACE_CONTRACT, ethers.MaxUint256); const marketplace = new ethers.Contract(MARKETPLACE_CONTRACT, MARKETPLACE_ABI, signer); await marketplace.createListing(assetId, ethers.parseEther(priceInSand)); } What's Included and Timelines
- Custom game logic development using TypeScript SDK.
- Configuration of LAND and ASSET ownership verification via Web3.
- Marketplace API integration for in-game NFT buy/sell.
- VoxEdit asset creation and publishing.
- Integration documentation and team training.
- Post-launch support.
A typical project takes 3 to 5 weeks. Basic functionality (ownership check, simple game logic) takes 1–2 weeks. Cost is calculated individually after we discuss your idea. Get a free project estimate — we'll respond within 24 hours. Contact us to discuss details.
For a deeper dive into SDK capabilities, refer to the official documentation at GitHub The Sandbox Game SDK.