TwentyFortyEight

A multiplayer version of 2048 built using Elixir/Phoenix.

Available to play at https://apearwin-2048.fly.dev/.

Development

A recent Elixir version and a running PostgreSQL instance are required for development. The simplest way to acquire these is via the provided Nix flake; if you have direnv installed run direnv allow and a development environment will be automatically available in your shell. PostgreSQL can be started in the foreground with devenv up.

Run mix setup to install Elixir dependencies and initialise the database.

Finally, run mix phx.server to start the development server.

Gameplay

The homepage lets you choose what kind of 2048 game you'd like to play, including:

• Board dimensions (number of rows and columns);
• How many obstacles to place on the board;
• Which numbers are placed on the board initially and during turns;
• What number is required to win.

After starting the game, you can copy the URL and share it with others (or open a separate browser tab to simulate another player). All players sharing a game can make moves in any order, and other players will see those moves in real time.

Up, down, left, and right movements are supported via the arrow keys, the hjkl keys, and the wasd keys. Playing on mobile isn't supported.

Code structure

The core gameplay runtime is independent of Phoenix and can in principle be driven by other interfaces, e.g. iex or a CLI client. The runtime is under the TwentyFortyEight.Game namespace.

• TwentyFortyEight.Game.Board: Stores the board size and individual cell values, and encapsulates the business logic of how moves affect the board and whether a board is unsolvable.
• TwentyFortyEight.Game.Engine: Operates on the full game state, including the board, number of turns, score, and whether the game has been won or lost.
• TwentyFortyEight.Game.Manager: A layer between an Engine and the database, providing persistence and retrieval of games.
• TwentyFortyEight.Game.Game: Persistence schema for storing game state to the database.
• TwentyFortyEight.Game.ManagerServer: A GenServer which passes messages between a Manager it holds and its own clients. It will shut down after several minutes of inactivity, triggering database persistence to allow subsequent restarts to pick up from where the game was left.

Phoenix components are under the TwentyFortyEightWeb namespace.

• TwentyFortyEightWeb.GameController: Presents the new-game form and handles its submission.
• TwentyFortyEightWeb.GameLive: A LiveView which creates or connects to Manager instances. It requests game state from the manager to display it, forwards key presses to the manager, and uses a PubSub topic for synchronising updates between players.

Finally, there's a bunch of Phoenix boilerplate I haven't tidied up!