Build Your Own Adventure

Background

Today we’re going to build an engine to support “choose your own adventure” games. Writing this engine will give us practice building an object oriented piece of software. Let’s have a look at what playing a game with this engine looks like.

Before you do anything

clone this repo to your computer
run npm install from with in the folder

To help you progress, we’ve written some test specs much like the ones you worked with in Test-First. You can run npm test to see the test suite run. To look at the specs source code, check out the test folder. We recommend you start by going through the specs in node.test.js, then connection.test.js, and then game.test.js.

Once you're through with all the specs, you can start building out player.js. The job of this file is to pull in the game source and tie it together with the inquirer library so that you if you run...

node player

...it will commence a command line interface for the game specified in game.source.js.

Example Game


Welcome. Do you choose to go left, or right
1) left
2) right
1

Ah, good choice. Good choice.

Had the adventurer said right, the game would have said “There be dragons there.”

Already we see that the game needs to support branching. It needs to respond to the user in different ways depending on what the user says.

Example Game Source

Checkout game.source.js in the main folder for an example game. See if you can piece together what’s going on! Then, try drawing out the game graph!

Components

We’re going to build this engine with several suggested components. We’ve set up files for each one in this project. We also wired them up to talk to each other. Here are some notes about them.

Node: A node is a single question or prompt in a game. Not to be confused with the technology node.js which we are also studying at Fullstack. This is particularly confusing because we have a file called node.js in this project, and because this project is built in node.
Connection: Connections represent the circumstances under which our game changes from one state to another. For the question “Would you like a cookie?” the connections might have the conditions “yes” and “no.”
Game: The game is what holds everything together. It's the interface that a game programer would use to construct these games. It exposes methods like addNode and connect. It keeps track of all the nodes in a javascript object.
Player: This is a component that is basically the “user interface” if we can call it that. It works with an npm package to present the current question to the user.
Game source: This is a file that uses the game class to build a game. You don't need to change this.

Order

We recommend you go through the specs in the following order:

test/node.test.js
test/connection.test.js
test/game.test.js

Once you're all done with those you can start working on player.js. At this point, the Game class should work as expected but has not yet been "plugged in" to work with a command line interface. There will be no specs for this final part. Instead, try to combine how Game instances work with how the inquirer library works. You will know everything is working if you can run node player.js to begin the command-line-choose-your-own-adventure example game.

The State Machine

Systems like the one we’re building are often called State Machines. Some of you may have studied these in school. For your benefit, take a minute to watch this video.