main.py

from turtle import Turtle, Screen
from random import randint
import time


STARTING_POSITION = [(0, 0), (-20, 0), (-40, 0)]
MOVE_DISTANCE = 20
UP = 90
DOWN = 270
LEFT = 180
RIGHT = 0


class Snake:
    def __init__(self):
        self.m_snake = []
        self.add_snake()
        self.m_head = self.m_snake[0]

    def snake_body(self, position): # Create a segment of the snake.
        new_turtle = Turtle("square")
        new_turtle.penup()
        new_turtle.color("white")
        new_turtle.goto(position)
        self.m_snake.append(new_turtle)

    def add_snake(self):  # Create 3 segments in the beginning.
        for position in STARTING_POSITION:
            self.snake_body(position)

    def grow(self):  # Add a new segment to the last segment of the snake.
        self.snake_body(self.m_snake[-1].position())

    def move_forward(self):
        for turtle_num in range(len(self.m_snake) - 1, 0, -1):
            new_x = self.m_snake[turtle_num - 1].xcor()
            new_y = self.m_snake[turtle_num - 1].ycor()
            self.m_snake[turtle_num].goto(new_x, new_y)
        self.m_head.forward(MOVE_DISTANCE)

    def up(self):
        if self.m_head.heading() != DOWN:
            self.m_head.setheading(UP)

    def down(self):
        if self.m_head.heading() != UP:
            self.m_head.setheading(DOWN)

    def left(self):
        if self.m_head.heading() != RIGHT:
            self.m_head.setheading(LEFT)

    def right(self):
        if self.m_head.heading() != LEFT:
            self.m_head.setheading(RIGHT)


class Beans(Turtle):
    def __init__(self):
        super().__init__()
        self.shape("circle")
        self.penup()
        self.shapesize(stretch_wid=0.5, stretch_len=0.5)
        self.color("yellow")
        self.speed("fastest")
        x_cor = randint(-280, 280)
        y_cor= randint(-280, 280)
        self.goto(x_cor, y_cor)
        self.refresh()

    def refresh(self):
        x_cor = randint(-280, 280)
        y_cor = randint(-280, 280)
        self.goto(x_cor, y_cor)


class ScoreRecord(Turtle):
    def __init__(self):
        super().__init__()
        self.score = 0
        self.color("white")
        self.penup()
        self.goto(0, 270)
        self.write(f"Score: {self.score}", align="center", font=("Arial", 24, "normal"))
        self.hideturtle()

    def add_score(self):
        self.score += 1
        self.clear()
        self.write(f"Score: {self.score}", align="center", font=("Arial", 24, "normal"))

    def game_over(self):
        self.goto(0,0)
        self.write("GAME OVER!", align="center", font=("Arial", 24, "normal"))


# Define the game screen.
screen = Screen()
screen.setup(width=600, height=600)
screen.bgcolor("black")
screen.tracer(0)

# Define objects.
snake = Snake()
bean = Beans()
score_record = ScoreRecord()

# Control the movement of the snake by keys.
screen.listen()
screen.onkey(snake.up, "Up")
screen.onkey(snake.down, "Down")
screen.onkey(snake.left, "Left")
screen.onkey(snake.right, "Right")

is_game_on = True
while is_game_on:
    screen.update()
    time.sleep(0.1)
    snake.move_forward()

    # Check if the snake get the bean.
    if snake.m_head.distance(bean) < 15:
        bean.refresh()
        snake.grow()
        score_record.add_score()

    # Detect the collision with walls.
    if snake.m_head.xcor() > 280 or snake.m_head.xcor() < -300 or snake.m_head.ycor() > 280 or snake.m_head.ycor() < -280:
        is_game_on = False
        score_record.game_over()

    # Detect the collision with tail.
    for body in snake.m_snake[1:]:  # Loop through the item in the snake.m_snake list other than the first one.
        if snake.m_head.distance(body) < 10:
            is_game_on = False
            score_record.game_over()

screen.exitonclick()