snake_game.py

import pygame
import random
from enum import Enum
from collections import namedtuple
import numpy as np

pygame.init()
font = pygame.font.SysFont('arial', 25)

# Reset
# Reward
# Play(action) -> Direction
# Game_iteration
# Is_collision

class Direction(Enum):
    RIGHT = 1
    LEFT = 2
    UP = 3
    DOWN = 4
    
Point = namedtuple('Point', 'x, y')

# RGB colors
WHITE = (255, 255, 255)
RED = (200,0,0)
GREEN1 = (62, 160, 85)
GREEN2 = (108, 187, 60)
BLACK = (0,0,0)

BLOCK_SIZE = 20
SPEED = 100

class SnakeGameAI:
    
    def __init__(self, w=640, h=480):
        self.w = w
        self.h = h
        # Init display
        self.display = pygame.display.set_mode((self.w, self.h))
        pygame.display.set_caption('Snake')
        self.clock = pygame.time.Clock()
        self.reset()
        

    def reset(self):
    ## Init game state
        # Starting Direction points to right
        self.direction = Direction.RIGHT
        
        # Snake will always spawn in middle of the screen
        self.head = Point(self.w/2, self.h/2)
        self.snake = [self.head, 
                    Point(self.head.x-BLOCK_SIZE, self.head.y),
                    Point(self.head.x-(2*BLOCK_SIZE), self.head.y)]
        
        self.score = 0
        self.food = None
        self.place_food()
        self.frame_iteration = 0


    def place_food(self):
        ## Randomly spawn food on map
        x = random.randint(0, (self.w-BLOCK_SIZE )//BLOCK_SIZE )*BLOCK_SIZE 
        y = random.randint(0, (self.h-BLOCK_SIZE )//BLOCK_SIZE )*BLOCK_SIZE
        self.food = Point(x, y)
        # If food is spawn in the snake body, place another on empty space
        if self.food in self.snake:
            self.place_food()
        

    def play_step(self, action):
        self.frame_iteration += 1

        # 1. Collect user input
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                pygame.quit()
                quit()
        
        # 2. Move
        self._move(action) # update the head
        self.snake.insert(0, self.head)
        
        # 3. Check if game over
        reward = 0
        game_over = False
        if self._is_collision() or self.frame_iteration > 100*len(self.snake):
            game_over = True
            reward = -10
            return reward, game_over, self.score
            
        # 4. place new food or just move
        # if food is eaten, place new food
        if self.head == self.food:
            self.score += 1
            reward = 10
            self.place_food()
        else:
            self.snake.pop()
        
        # 5. update ui and clock
        self._update_ui()
        self.clock.tick(SPEED)
        # 6. return game over and score
        return reward, game_over, self.score
    

    def _is_collision(self, pt=None):
        if pt is None:
            pt = self.head
        # hits boundary
        if pt.x > self.w - BLOCK_SIZE or pt.x < 0 or pt.y > self.h - BLOCK_SIZE or pt.y < 0:
            return True
        # hits itself
        if pt in self.snake[1:]:
            return True
        
        return False
        

    def _update_ui(self):
        self.display.fill(BLACK)
        
        for pt in self.snake:
            pygame.draw.rect(self.display, GREEN1, pygame.Rect(pt.x, pt.y, BLOCK_SIZE, BLOCK_SIZE))
            pygame.draw.rect(self.display, GREEN2, pygame.Rect(pt.x+4, pt.y+4, 12, 12))
            
        pygame.draw.rect(self.display, RED, pygame.Rect(self.food.x, self.food.y, BLOCK_SIZE, BLOCK_SIZE))
        
        text = font.render("Score: " + str(self.score), True, WHITE)
        self.display.blit(text, [0, 0])
        pygame.display.flip()
        

    def _move(self, action):
        # [straight, right, left]

        clock_wise = [Direction.RIGHT, Direction.DOWN, Direction.LEFT, Direction.UP]
        current_index = clock_wise.index(self.direction)

        if np.array_equal(action,[1, 0, 0]):
            new_dir = clock_wise[current_index] # No change Direction
        elif np.array_equal(action,[0, 1, 0]):
            next_index = (current_index + 1) % 4 # Turn right with 90 degrees
            new_dir = clock_wise[next_index]
        elif np.array_equal(action,[0, 0, 1]):
            next_index = (current_index - 1) % 4 # Turn left with 90 degrees
            new_dir = clock_wise[next_index]

        self.direction = new_dir
            
        x = self.head.x
        y = self.head.y
        if self.direction == Direction.RIGHT:
            x += BLOCK_SIZE
        elif self.direction == Direction.LEFT:
            x -= BLOCK_SIZE
        elif self.direction == Direction.DOWN:
            y += BLOCK_SIZE
        elif self.direction == Direction.UP:
            y -= BLOCK_SIZE
            
        self.head = Point(x, y)