carlbeek / gym-snake

An OpenAI gym environment made for RL

gym-snake

Created in response to OpenAI's Requests for Research 2.0

Attribution

This environment is a modified version of grantsrb's Gym Snake implementation but with only a single snake & one piece of food at a given time. Furthermore, the state is not the colour of all of the pixels, but rather the snake and food's positions.

Description

gym-snake is a multi-agent implementation of the classic game snake that is made as an OpenAI gym environment.

This repo offers the snake-v0 environment. snake-v0 is the classic snake game. See the section on SnakeEnv for more details.

Many of the aspects of the game can be changed for both environments. See the Game Details section for specifics.

Dependencies

• pip
• gym
• numpy
• matplotlib

Installation

1. Clone this repository
2. Navigate to the cloned repository
3. Run command $ pip install -e ./

Using gym-snake

After installation, you can use gym-snake by making one of two gym environments.

SnakeEnv

Use gym.make('snake-v0') to make a new snake environment with the following default options (see Game Details to understand what each variable does):

grid_size = [15,15]
unit_size = 10
unit_gap = 1
snake_size = 3

Game Details

You're probably familiar with the game of snake. This is an OpenAI gym implementation of the game.

Rewards

A +1 reward is returned when a snake eats a food.

A -1 reward is returned when a snake dies.

No extra reward is given for victory snakes in plural play.

Game Options

• grid_size - An x,y coordinate denoting the number of units on the snake grid (width, height).
• unit_size - Number of numpy pixels within a single grid unit.
• unit_gap - Number of pixels separating each unit of the grid. Space between the units can be useful to understand the direction of the snake's body.
• snake_size - Number of body units for each snake at start of game
• random_init - If set to false, the food units initialize to the same location at each reset.

Each of these options are member variables of the environment and will come into effect after the environment is reset.

env = gym.snake('snake-v0')
observation = env.reset()

This will create a vanilla snake environment.

Environment Parameter Examples

Below is the default setting for snake-v0 play, 15x15 unit grid.

Below is env.unit_gap == 0 and a 30x30 grid.

Below set env.unit_gap half the unit size with a 15x15 sized grid.

General Info

The snake environment has three main interacting classes to construct the environment. The three are a Snake class, a Grid class, and a Controller class. Each holds information about the environment, and each can be accessed through the gym environment.

import gym
import gym_snake

# Construct Environment
env = gym.make('snake-v0')
observation = env.reset() # Constructs an instance of the game

# Controller
game_controller = env.controller

# Grid
grid_object = game_controller.grid
grid_pixels = grid_object.grid

# Snake
snake = game_controller.snake

Coordinates

The units of the game are made to take up multiple pixels within the grid. Each unit has an x,y coordinate associated with it where (0,0) represents the uppermost left unit of the grid and (grid_object.grid_size[0], grid_object.grid_size[1]) denotes the lowermost right unit of the grid. Positional information about snake food and snake's body is encoded using this coordinate system.

Snake Class

This class holds all pertinent information about an individual snake. Useful information includes:

# Action constants denote the action space.
snake_object1.UP # Equal to integer 0
snake_object1.RIGHT # Equal to integer 1
snake_object1.DOWN # Equal to integer 2
snake_object1.LEFT # Equal to integer 3

# Member Variables
snake_object1.direction # Indicates which direction the snake's head is pointing; initially points DOWN
snake_object1.head # x,y Coordinate of the snake's head
snake_object1.head_color # A pixel ([R,G,B]) of type uint8 with an R value of 255
snake_object1.body # deque containing the coordinates of the snake's body ordered from tail to neck [furthest from head, ..., closest to head]

Grid Class

This class holds all pertinent information about the grid that the snakes move on. Useful information includes:

# Color constants give information about the colors of the grid
# Each are ndarrays with dtype uint8
grid_object.BODY_COLOR # [1,0,0] Color of snake body units
grid_object.HEAD_COLOR # [255, (i+1)*10, 0] Color of snake head units. i is the index of the snake.
grid_object.FOOD_COLOR # [0,0,255] Color of food units
grid_object.SPACE_COLOR # [0,255,0] Color of blank space

# Member Variables
grid_object.unit_size # See Game Options
grid_object.unit_gap # See Game Options
grid_object.grid_size # See Game Options
grid_object.grid # Numpy [R,G,B] pixel array of game

Controller Class

The Controller holds a grid object and an array of snakes that move on the grid. The Controller class handles the game logic between the snake and the grid. Actions are taken through this class and initialization parameters within this class dictate the initial parameters of the grid and snake object in the game. Useful information includes:

# Member variables
game_controller.grid # An instance of the grid class for the game
self.snake # A snake object. If a snake dies, it is erased and it becomes None.