main.py

from tkinter import *

import random

GAME_WIDTH = 700
GAME_HEIGHT = 700
speed = 120
SPACE_SIZE = 50
BODY_PARTS = 3
SNAKE_COLOR = "#00FF00"
FOOD_COLOR = "#FF0000"
BACKGROUND_COLOR = "#000000"

#Self-explanatory
class Snake:

    def __init__(self):
        self.body_size = BODY_PARTS
        self.coordinates = []
        self.squares = []

        for i in range(0, BODY_PARTS):
            self.coordinates.append([0, 0])

        for x, y in self.coordinates:
            square = canvas.create_rectangle(x, y, x + SPACE_SIZE, y + SPACE_SIZE, fill=SNAKE_COLOR, tag="snake")
            self.squares.append(square)

#Class for the food eaten by the snake
class Food:
    def __init__(self):

        x = random.randint(0, (GAME_WIDTH // SPACE_SIZE)-1) * SPACE_SIZE
        y = random.randint(0, (GAME_HEIGHT // SPACE_SIZE) - 1) * SPACE_SIZE

        self.coordinates = [x, y]

        canvas.create_oval(x, y, x + SPACE_SIZE, y + SPACE_SIZE, fill=FOOD_COLOR, tag="food")

#movement mechanism for the snake
def next_turn(snake, food, speed):

    x, y = snake.coordinates[0]

    if direction == "up":
        y-= SPACE_SIZE

    elif direction == "down":

        y+=SPACE_SIZE

    elif direction == "left":
        x-=SPACE_SIZE

    elif direction == "right":
        x+=SPACE_SIZE

    snake.coordinates.insert(0, (x, y))

    square = canvas.create_rectangle(x, y, x + SPACE_SIZE, y + SPACE_SIZE, fill=SNAKE_COLOR)

    snake.squares.insert(0, square)

    if x == food.coordinates[0] and y == food.coordinates[1]:

        global score

        score += 1

        label.config(text="Score={}".format(score))

        canvas.delete("food")

        food = Food()

        if(speed > 10):
            speed -=10

    else:

        del snake.coordinates[-1]

        canvas.delete(snake.squares[-1])

        del snake.squares[-1]

    if check_collisions(snake):
        game_over()
    else:
        window.after(speed, next_turn, snake, food, speed)

#changes direction depending on arrow keys
def change_direction(new_direction):

    global direction

    if new_direction == 'left':
        if direction != 'right':
            direction = new_direction
    elif new_direction == 'right':
        if direction != 'left':
            direction = new_direction
    if new_direction == 'up':
        if direction != 'down':
            direction = new_direction
    if new_direction == 'down':
        if direction != 'up':
            direction = new_direction

#checks whether the snake has collided with the walls or itself
def check_collisions(snake):

    x,y = snake.coordinates[0]

    if x < 0 or x >= GAME_WIDTH:
        return True
    elif y < 0 or y >= GAME_HEIGHT:
        return True

    for body_part in snake.coordinates[1:]:
        if x == body_part[0] and y == body_part[1]:
            print("GAME OVER")
            return True

    return False

#resets all the values and restarts the game
def restart_game():
    global score, direction
    score = 0
    direction = 'down'
    label.config(text="Score:{}".format(score))
    canvas.delete("game_over")
    canvas.delete("food")
    snake.coordinates = []
    snake.squares = []
    for i in range(0, BODY_PARTS):
        snake.coordinates.append([0, 0])
    snake.__init__()
    food.__init__()
    next_turn(snake, food, speed)

#ends the game if snake touches the borders or itself
def game_over():

    canvas.delete(ALL)
    canvas.create_text(canvas.winfo_width()/2, canvas.winfo_height()/2,
                       font =('consolas',70), text="GAME OVER", fill="red", tag="game_over")

    canvas.create_text(canvas.winfo_width() / 2, canvas.winfo_height() / 2 + 100,
                       font=('consolas', 30), text="Press 'R' to retry", fill="white", tag="game_over")

#key press method to restart the game
def key_press(event):
    if event.char.lower() == 'r':
        restart_game()

window = Tk()
window.title("Snake game")
window.resizable(False, False)

score = 0
direction = 'down'

label = Label(window, text = "Score:{}".format(score), font=('consolas', 40))
label.pack()

canvas = Canvas(window, bg=BACKGROUND_COLOR, height=GAME_HEIGHT, width=GAME_WIDTH)
canvas.pack()

#Binds the key to the key press
window.bind('<Key>', key_press) 

window.update()

window_width = window.winfo_width()
window_height = window.winfo_height()
screen_width = window.winfo_screenheight()
screen_height = window.winfo_screenheight()

x = int((screen_width/2) - (window_width/2))
y = int((screen_height/2) - (window_height/2))

window.geometry(f"{window_width}x{window_height}+{x}+{y}")

window.bind('<Left>', lambda event: change_direction('left'))
window.bind('<Right>', lambda event: change_direction('right'))
window.bind('<Up>', lambda event: change_direction('up'))
window.bind('<Down>', lambda event: change_direction('down'))

snake = Snake()
food = Food()

next_turn(snake, food, speed)


window.mainloop()