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Game documentation

Here we have a traditional tic-tac-toe game to be played by two people in-browser. Players are given instructions to get them started following the traditional rules of the game:

  1. Players alternate marking spaces on the board.
  2. If a player fills a full row, full column, or major diagonal (top corner to opposite bottom corner) with their marker, they win!
  3. If all spaces are filled without a winner, the game is over and must be reset.

Project setup

Playing the game

Simply load the game page (index.html) in a browser. The game uses only client-side languages that browsers understand, so the browser will take care of everything.

Developer setup

This app is built with the new ES6 version of Javascript and the Sass CSS pre-processor (SCSS-style). To generate the backwards-compatible Javascript and true CSS, we're using the Grunt build tool. You'll need the npm, the Node.js package manager, installed on your local environment.

After downloading game files, run npm install in your terminal to install the node_modules directory and project dependencies. Once that is complete, run the command grunt and your terminal will start watching for Javascript or SCSS changes to update the game code.

You can also run grunt scss to run the CSS build once or grunt scripts to run the Javascript build once.

The game Javascript will be tested against ESLint rules set by an included .eslintrc file. The SCSS will also be checked with scss-lint, a Ruby gem, using the .scss-lint.yml file. It adds Ruby as an additional dependency, but in the context of my development process it wasn't anything new. Per the linter instructions:

  1. Please make sure you have ruby installed: ruby -v
  2. Install the scss-lint gem globally by running: gem update --system && gem install scss-lint

Thought process

In building the game, two major goals of mine were to write the Javascript very legibly for other developers and to make it as flexible to changes in the game. To the first point, all game functions are broken out individually for reuse as needed. Each function has a limited purpose that I tried to make clear with its name and code documentation. At any point where I saw code replication or problematic legibility, I moved that code into a function or variable, such as with the very verbose rowIdx/colInx variables used to find array indexes for a following conditional statement.

Traditionally, tic-tac-toe games are played in three by three grids, hence the name of the game. Initially, to focus on the core mechanics, I wrote out the win scenarios in the rowOrCol, diagWin1, and diagWin2 variables by hand. With only three rows and columns the win scenarios were limited so this wasn't too long. I knew right away that it would be better if I didn't use "magic numbers" hard-coded, even if the three by three grid is the standard.

I also thought that it would be great if the player could choose the size of the grid they wanted to play on. If they wanted an intense game, they could have five by five grids with 25 squares to fill. In mentioning this to a friend, she reminded me that more squares increased the likelihood of a "game over" scenario. I decided against exposing the option to change the grid, but I did refactor my JS to allow the possibility. All win scenarios are now generated based on a gridLength variable that could potentially be changed. At this moment, this variable is also set based on the HTML markup, so all someone would really need to do is expand the grid via HTML.

This project also game me opportunity to use some ES6 features that I hadn't previously. This included creating a Javascript class for the players, so functionality could easily be added to generate new players based on user inputs. I also used the Object.assign() function, which is a fantastically simple way to clone an object--in this case the row and column win scenario object. Since the Babel ES6 compiler only converts the new syntax, I loaded this new addition to the Object prototype with the great conditional polyfill service, Since Object.assign() is the only new feature I needed, I limited my use of to that once feature, avoiding needless bloat.

On the HTML markup side of things, I kept it fairly simple. All content other than the game name is loaded via Javascript based on the game status. One choice I made was to use the button element for the board squares. This could have been built with the squares as div, li, or a elements, but I thought that button was most appropriate for semantic and accessibilty reasons. It comes "out of the box" ready for interaction and also can be easily disabled with the disabled attribute once the space is used.

Finally, in the CSS I decided to use the new CSS Grid spec for the game board. The spec is now supported in all major modern browsers and given that the board is literally a grid, it seemed an appropriate use. The grid-template property on the board would need to be changed if the HTML markup was expanded to increase the grid size.

Enhancement ideas

  • Track wins by each player across games in a single session, alternating the starting player.
  • Save the game state by setting a cookie to associate with game status.
  • Let the players optionally enter their names (for the win message) and choose alternate marker symbols. I would not want to require this or have it visible automatically since it might unnecessarily clutter the interface.
  • Customize some SVG animations for win and game over messages.


JS-built tic-tac-toe game.



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