snake_pygame.py

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

pygame.init()
arial = pygame.font.Font(pygame.font.match_font('arial'), 14)
font = arial
#font = pygame.font.Font('arial.ttf', 25)

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 = (0, 255, 0)
GREEN2 = (0, 255, 100)
BLACK = (0,0,0)

BLOCK_SIZE = 20
SPEED = 40

class SnakeGameAI:

    def __init__(self, w=640, h=480):
        #width and height of gui
        self.w = w
        self.h = h
        self.display = pygame.display.set_mode((self.w, self.h))
        pygame.display.set_caption('Snake AI')
        self.clock = pygame.time.Clock()
        self.reset()

    def reset(self):
        #init state
        self.direction = Direction.RIGHT
        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.food = Point(x,y)
        self._place_food()
        self.frame_iteration = 0

    def _place_food(self):
        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)

    def play_step(self, action):
        self.frame_iteration += 1
        #collect user input
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                pygame.quit()
                quit()
        
        #move
        self._move(action) #update the head
        self.snake.insert(0, self.head)
        
        #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

        #place new food or just move
        if self.head == self.food:
            self.score += 1
            reward = 10
            self._place_food()
        else:
            self.snake.pop()
        
        #update ui and clock
        self._update_ui()
        self.clock.tick(SPEED)
        #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]
        idx = clock_wise.index(self.direction)

        if np.array_equal(action, [1, 0, 0]):
            new_dir = clock_wise[idx] #no change
        elif np.array_equal(action, [0, 1, 0]):
            next_idx = (idx + 1) % 4
            new_dir = clock_wise[next_idx] #right turn r -> d -> l -> u
        else: #[0, 0, 1]
            next_idx = (idx - 1) % 4
            new_dir = clock_wise[next_idx] #left turn r -> u -> l -> d

        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)