Scaffold server

Let's create a new folder and name it, for example leap-word-game:

mkdir leap-word-game

Let's move inside of it and make two more folders

cd leap-word-game
mkdir universal client

If you haven't installed Express in previous step you can do it now by running:

npm install express-generator -g

Next let's init our express server:

express server

This will create a new folder called server with express scaffold inside of it. Let's go inside of it and install project dependencies:

cd server
npm install

Wait until installation is finished. After that you will need to install several additional packages:
- dotenv will be used to inject environmental variables using .env file
- got will handle our http-request for faucet
- corser to handle CORS request from our front-end
- ethereumjs-util will provide ripemd160 method to create contract address
- leap-core supplies methods and data structures to interact with Leap network
- random-words will generate us random words for each round
- clipboardy for handy clipboard methods
- openzeppelin-solidity for IERC20 contract
- truffle to compile our smart contracts

npm install dotenv got ethereumjs-util ethers leap-core random-words corser
npm install -dev clipboardy openzeppelin-solidity
npm install -g truffle nodemon

If you on Windows and encounter and errors during the process, try to install windows-build-tools module then run npm install again

Ensure that your terminal is currently inside server folder and then init truffle part (agree to install inside non-empty folder). This will create two folders "contracts" and "migrations"

truffle init

Reply with "y" when Truffle will say that folder is not empty and aks if you want to continue.

After that try to spin up server

nodemon start

You can access index page at http://localhost:3000

Add corser

In order to allow our server to accept cross-origin requests from front-end client we need to activate CORS handling. We will use corser Express middleware for this. Edit app.js file in the root of server folder

// On line 6 add corser to list of imported modules
var corser = require('corser');

// Then activate it on line 17 after app.use(logger('dev'));


To use wallet on server side we will need to have one and get some funds into it. You can skip this step

Let's create folder tools in the root of server and put generateWallet.js file into it:

const ethers = require('ethers/index');
const clipboardy = require('clipboardy/index');

async function main() {
  let wallet = ethers.Wallet.createRandom();
  console.log("Mnemonic:", wallet.mnemonic);
  console.log("We also wrote put in your clipboard. You welcome :)");


Open terminal inside server folder and run:

node tools/generateWallet

Script will create new mnemonic, output it to screen and also put it into your clipboard.

Create new .env file in the root of server folder and put contents of your clipboard after WALLET_MNEMONIC variable:


Security Note: Don't ever put your .evn file in repository as it contains crucial information, which can be used to transfer ALL your wallet funds without your knowledge. Keep this somewhere safe. You will be able to setup this variables later, when you deploy your server

Create new file inside root of server folder and call it config.js. We will use it read values from our .env file in a convenient way

const dotenv = require("dotenv");

// Get WALLET_MNEMONI from .env file
const { WALLET_MNEMONIC } = process.env;

module.exports = {


In root folder of our project go to universal and create new file config.js. We will use it to provide token address, RPC url and wallet mnemonic for our server. In this tutorial we gonna use LEAP token and RPC on staging server. Changing it to testnet will be just a matter of updating RPC and TOKEN_ADDRESS variables

//const RPC_URL = ""; // Testnet RPC
//const TOKEN_ADDRESS = "0xD2D0F8a6ADfF16C2098101087f9548465EC96C98"; // Testnet LEAP

const RPC_URL = ""; // Staging RPC
const TOKEN_ADDRESS = "0x0666eBbF26CDE07EA79FeCAe15e5f18394EBC149"; // Staging LEAP

module.exports = {

Next step we will create our smart contract - which we would further refer as "spending condition" - and compile it.