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Bucklescript-Tea Game OverBots Pt.1 - Setup

I've been meaning to make a more comprehensive bucklescript-tea tutorial / example project for a while, and I had an older one partially done but it is a bit out of date now so I've decide to make one anew instead, and to facilitate this I've decided to make a game. Right now most of the 'reference information' about bucklescript-tea is identical to Elm's documentation, so seeing the real-world use of it would be more generically useful.

If you are curious why I am using Bucklescript as the language, take a look at my past post of Why Use Bucklescript.

I've decided to make a little incremental game, they are addictive to me and I enjoy them, however I am no game designer, I am only a programmer, so if anyone has ideas on how it should play or work or anything then do not hesitate to say either via comments on these posts, my email, or any other way that I am easily contacted. :-)

Why did I name it OverBots? No clue, first thing that popped up in mind. If there is a really good and appropriate name then please suggest it. :-)

Why Bucklescript-TEA?

Feel free to skip this section and jump down to What is an incremental game? if you know Elm already. Basically Bucklescript-TEA uses The Elm Architecture but placed into the significantly more powerful language of OCaml, however most of the syntax and calls remain identical, you can 'almost' copy Elm code in to Bucklescript-TEA with minor formatting changes. :-)

Basically TEA is designed to make complex web apps that remain maintainable, fast, and reusable. You separate your data storage into a defined and segmented area, your view in another, and your updating in yet another, all kept distinct. The basic structure of a TEA application is as follows:

Your model definition:

type model = {
  x : int
  y : string
  z : SomethingElse.t

This is where all your data is stored, the only place, can add whatever fields you wish, can link to type definitions that are defined or that you define elsewhere and link them in here, everything eventually ends up here and is stored here.

Your message type:

type msg =
| Blah
| Blorp of int

This will be a type of your choosing that you will give to your updater to perform actions, such as when a button is clicked or a timer elapses.

Your update 'loop':

let update model msg =
  model, Cmd.none

The update function takes the model structure and a message of the msg type of your own choosing above. You update your model based on the message and return the updated model and an optional 'Cmd'. Commands are used to 'do' something out of the main app interface, such as update the address bar as one example.

Your Subscriptions:

let subscriptions model =

Subscriptions are things like listening to events on the DOM or a timer or so, you can register and unregister to subscriptions based on your model state.

Your view creator:

let view model =
  [ text "Hello World!"

The view function takes your model whenever it changes, creates a virtual DOM based on that model and returns it. The internal virtual DOM implementation does a diff between this and the last state and only updates the physical DOM where and when it is necessary, thus making this overall a very cheap operation, easily composable by calling more view functions of your own choosing, so you could, for example, have a button function that returns the vdom for a button that you just call where you need it.

With these parts you have a very composable and easy to reason about application that is wonderfully easy to debug while also minimizing the time needed to debug as you can easily find what message happened that caused the model to change and see exactly what occurred.

What is an incremental game?

The 'original' and probably most popular Incremental Game is Cookie Clicker, though the genre has now grown to encompass a variety of similar style, many of which have become time based that players min/max to increase their score. They tend to be quite simple and most are indeed purely text based. This one will not be so clicking repeatedly based but will be more about pure resource acquisition as this is a more challenging code design.

Initial Setup

Of course go ahead and have npm/node installed, as well as the requirements for bucklescript installation (nothing really on windows as bucklescript is pre-built unless you are wanting to build it manually of course, on linux/mac you need cmake and the necessary build systems to build bucklescript). At this point let's get started by setting up the project.

╭─overminddl1@snip ~/ocaml
╰─➤  mkdir overbots
╭─overminddl1@snip ~/ocaml
╰─➤  cd overbots
╭─overminddl1@snip ~/ocaml/overbots
╰─➤  npm init
This utility will walk you through creating a package.json file.
It only covers the most common items, and tries to guess sensible defaults.

See `npm help json` for definitive documentation on these fields
and exactly what they do.

Use `npm install <pkg> --save` afterwards to install a package and
save it as a dependency in the package.json file.

Press ^C at any time to quit.
name: (overbots)
version: (1.0.0) 0.0.1
description: OverBots Incremental Game
entry point: (index.js)
test command:
git repository:
keywords: bucklescript bucklescript-tea
author: OvermindDL1
license: (ISC) GPL-3.0
About to write to /home/overminddl1/ocaml/overbots/package.json:

  "name": "overbots",
  "version": "0.0.1",
  "description": "OverBots Incremental Game",
  "main": "index.js",
  "devDependencies": {
    "bs-platform": "^1.7.3",
    "bucklescript-tea": "^0.3.2"
  "dependencies": {},
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  "repository": {
    "type": "git",
    "url": "git+"
  "keywords": [
  "author": "OvermindDL1",
  "license": "GPL-3.0",
  "bugs": {
    "url": ""
  "homepage": ""

Is this ok? (yes)

╭─overminddl1@snip ~/ocaml/overbots
╰─➤  npm install --save-dev bs-platform bucklescript-tea
..snip tons and tons of stuff as it installs and compiles
├── bs-platform@1.7.3
└── bucklescript-tea@0.3.2

╭─overminddl1@snip ~/ocaml/overbots
╰─➤  git init
Initialized empty Git repository in /home/overminddl1/ocaml/overbots/.git/
╭─overminddl1@snip ~/ocaml/overbots  ‹master*›
╰─➤  git remote add origin

At this point open it is not good to open a text editor of your choice. I tend to swap between Atom and Spacemacs depending on how I feel. It is now time to create the bucklescript scafffolding. Right now we need to make the bsconfig.json file ourselves but Bucklescript has plans to make its own creation commands later to make this part easier, however this part is not hard at all currently so let's make up the bsconfig.json file:

    "name": "overbots",
    "sources": { "dir" : "src"},
    "package-specs": ["es6"],
    "bs-dependencies": ["bucklescript-tea"],
    "generate-merlin": true

I also like to have convenience commands for npm so I'm changing my "scripts" section in npm's package.json to become:

  "build": "bsb -make-world",
  "prewatch": "npm run build",
  "watch": "bsb -w",
  "test": "echo \"Error: no test specified\" && exit 1"

And now I make my main entrance file at src/ and I put in it this, the basic bucklescript-tea program structure:

open Tea

type msg =
  | NothingYet
  [@@bs.deriving {accessors}]

type model = {
  notUsedYet : int;

let init () =
  let model ={
    notUsedYet = 42;
  } in
  (model, Cmd.none)

let update model = function
  | NothingYet -> (model, Cmd.none)

let subscriptions _model =

let view model =
  let open Html in
    [ text (string_of_int model.notUsedYet)

let main =
  App.standardProgram {

And we can compile it with npm run build or we can run the auto-builder/watcher with npm run watch (and Ctrl+c to cancel the auto-building/watching). It should compile cleanly with the output javascript going in to the lib/js directory. Speaking of, let's go ahead and compile all that output together with rollup.js

Production Generation

I want to be able to bundle this out to optimized javascript for easy running in the browser, and one of the best bundlers out is rollup.js, so let's use that one:

╭─overminddl1@snip ~/ocaml/overbots  ‹master*›
╰─➤  npm install --save-dev rollup-plugin-node-resolve rollup-watch rollup
overbots@0.0.1 /home/overminddl1/ocaml/overbots
├── rollup@0.41.6
├── rollup-plugin-node-resolve@3.0.0
└── rollup-watch@3.2.2

I also want to use npm itself as the build system instead of using something dreadfully slow like webpack or so, thus let's install a few helpers:

╭─overminddl1@snip ~/ocaml/overbots  ‹master*›
╰─➤  npm install --save-dev npm-run-all
overbots@0.0.1 /home/overminddl1/ocaml/overbots
└─┬ npm-run-all@4.0.2
  ├ Snip a mess of stuff...

And to use it let's change the package.json "scripts" section to be this:

  "build:bsb": "bsb -make-world",
  "build:js": "rollup -c",
  "build": "run-s build:bsb build:js",
  "watch:bsb": "bsb -w",
  "watch:js": "rollup -c -w",
  "prewatch": "run-s build",
  "watch": "run-p watch:bsb watch:js",
  "test": "echo \"Error: no test specified\" && exit 1"

And since I do not like to put tons of config options on the commandline in script, let's put the rollup options in a rollup.config.js file in the root directory of the project and put this in it:

export default {
  entry: 'lib/es6/overbots.js',
  format: 'iife',
  dest: '/release/overbots-bundled.js'

And now we can run npm run build to build it all to a final bundled file, or run npm run watch to do the same on every save of source files. For the purpose of testing I'm also going to make a release/dev.html file with this so I can load it in the browser for ease of development:

  <meta content="text/html;charset=utf-8" http-equiv="Content-Type">
  <meta content="utf-8" http-equiv="encoding">
  <script src="overbots-bundled.js"></script>
    var app = overbots.main(document.body);
  }, 1)

And loading that up in the browser I just see a 42 printed inside a div and that is all. :-)


I also want to use SCSS for CSS as it makes dealing with CSS to be far more maintainable, thus:

╭─overminddl1@snip ~/ocaml/overbots  ‹master*›
╰─➤  npm install --save-dev node-sass nodemon postcss autoprefixer postcss-cli
├── autoprefixer@7.0.1
├── node-sass@4.5.2
├── nodemon@1.11.0
├── postcss@6.0.1
└── postcss-cli@4.0.0

And changing my package.json `"scripts" block to be:

  "build:bsb": "bsb -make-world",
  "build:js": "rollup -c",
  "build:scss": "node-sass --include-path scss scss/overbots.scss css/overbots.css",
  "build:css": "postcss --use autoprefixer -o release/overbots.css css/overbots.css",
  "build": "run-s build:bsb build:js build:scss build:css",
  "watch:bsb": "bsb -w",
  "watch:js": "rollup -c -w",
  "watch:scss": "nodemon -e scss -x \"npm run build:scss\"",
  "watch:css": "nodemon -e css -x \"npm run build:css\"",
  "prewatch": "run-s build",
  "watch": "run-p watch:bsb watch:js watch:scss watch:css",
  "test": "echo \"Error: no test specified\" && exit 1"

And I also added a stylesheet to it in the dev.html file in the head above the script tags:

<link rel="stylesheet" type="text/css" href="overbots.css">

As well as creating an empty file at scss/overbots.scss.

This will be good for the initial setup, development, and etc. I think, next time let's start making the game!


You can access the output of this post at Overbots Pt1.

And the source is on the Overbots Github Pt1.

Check out this entire series via the Overbots tag.


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