Crystal Snake

This is a Battle Snake project written in Crystal using Kemal

I strongly recommend reading the docs in You'll find detailed information on classes and methods there :)

I wrote a few blog posts about this project. Check out the first one here.


You'll need Crystal, Postgres 14 & Redis locally. The app uses for ease of development.

# Install dependencies
shards install

# Start development server in port 8080 with live reload
make sam dev

# Run tests
make sam test

# Use a custom strategy
STRATEGY="ChaseClosestFood" make sam dev


The app can be configured using an .env file (example below)


For local development I use the BattleSnake CLI with the local server running. A basic example looks like this:

# Solo game
battlesnake play -W 11 -H 11 --name dev --url http://localhost:8080 -g solo -v

# 1v1 against itself (you should be able to use any public snake if you know their URL)
battlesnake play -W 11 -H 11 --name dev --url http://localhost:8080  --name dev2 --url http://localhost:8080 -v

Strategies & Architecture

The server is built on the src/ file and you can choose to use any of the available strategies (list available here).

To start hacking a new one create a new strategy (in that folder) that inherits from Stategy::Base. They're all initialized with a BattleSnake::Context and you call #move method to chose a move to respond with (the method your logic will live). You can re-use strategies within each other, i.e. Strategy::ChaseClosestFood uses the Strategy::RandomValid strategy when reachable food doesn't exist on the board.

You can also use Strategy::Utils class methods like Strategy::Utils.a_star which implements the A* Search Algorithm (list of Utils helper methods available).


I'm currently using DigitalOcean App Platform. The Dockerfile is detected and deployed on their cheapest tier. It "should work" in lots of other platforms with this setup, but open an issue if you need help troubleshooting or to discuss other solutions.


ENV variables are used to customize your snake


  1. Fork it (
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create a new Pull Request