How to make page url like this: ‘…/games/firstGame’ where games is a parent page

I am trying to build a node.js following the heroku tutorial. I currently have this:

const express = require('express')
const path = require('path')
const PORT = process.env.PORT || 5000

express()
    .use(express.static(path.join(__dirname, 'public')))
    .set('views', path.join(__dirname, 'views'))
    .set('view engine', 'ejs')
    .get('/game', (req, res) => res.render('pages/game/game'))
    **.get('/game/firstGame', (req, res) => res.render('pages/game/game-firstGame'))**
    .listen(PORT, () => console.log(`Listening on ${ PORT }`))

However, this does not work because everytime I access this page with the window location directed to

https://.../game/firstGame

The heroku app will give me: Internal Server Error

Plus, the Firefox browser tells that I lack the file firstGame although I specified to render the file game-firstGame file