A simple clone of the popular game "Snake" I made shortly after getting my Raspberry Pi and diving into Linux for the first time several years ago.

snakeclone.py

#!/usr/bin/env python

"""
A simple clone of the game Snake made to expose myself to Python/Pygame. Inspired by the guide in
the Raspberry Pi User Guide by Eben Upton and Gareth Halfacree, though I did make some changes
based on my preferences and coding style.
"""

import pygame, sys, time, random
from pygame.locals import *

pygame.init()
fpsClock = pygame.time.Clock()

playSurface = pygame.display.set_mode((640, 480))
pygame.display.set_caption('Raspberry Snake')

red = pygame.Color(255, 0, 0)
black = pygame.Color(0, 0, 0)
white = pygame.Color(255, 255, 255)
grey = pygame.Color(150, 150, 150)

# Initialization
snakePosition = [100,100]
snakeSegments = [[100,100],[80,100],[60,100]]
raspberryPosition = [300,300]
raspberrySpawned = 1
direction = 'right'
changeDirection = direction

# Game Over definition; called whenever the snake hits a boundary or collides with itself.
def gameOver():
    gameOverFont = pygame.font.Font('freesansbold.ttf', 72)
    gameOverSurf = gameOverFont.render('Game Over', True, grey)
    gameOverRect = gameOverSurf.get_rect()
    gameOverRect.midtop = (320, 10)
    playSurface.blit(gameOverSurf, gameOverRect)
    pygame.display.flip()
    time.sleep(5)
    pygame.quit()
    sys.exit()

# Main game loop
while True:
    # Event handler loop
    for event in pygame.event.get():
        if event.type == QUIT:
            pygame.quit()
            sys.exit()
        elif event.type == KEYDOWN:
            if event.key == K_RIGHT or event.key == ord('d'):
                changeDirection = 'right'
            if event.key == K_LEFT or event.key == ord('a'):
                changeDirection = 'left'
            if event.key == K_UP or event.key == ord('w'):
                changeDirection = 'up'
            if event.key == K_DOWN or event.key == ord('s'):
                changeDirection = 'down'
            if event.key == K_ESCAPE:
                pygame.event.post(pygame.event.Event(QUIT))

    # The following conditionals ensure that the snake does not commit suicide by moving
    # backwards and colliding with itself.
    if changeDirection == 'right' and not direction == 'left':
        direction = changeDirection
    if changeDirection == 'left' and not direction == 'right':
        direction = changeDirection
    if changeDirection == 'up' and not direction == 'down':
        direction = changeDirection
    if changeDirection == 'down' and not direction == 'up':
        direction = changeDirection

    if direction == 'right':
        snakePosition[0] += 20
    if direction == 'left':
        snakePosition[0] -= 20
    if direction == 'up':
        snakePosition[1] -= 20
    if direction == 'down':
        snakePosition[1] += 20

    # The following five lines of code allow the snake to move and grow. A new segment is added in front
    # of the snake whenever it moves; if it does not collide with the raspberry/food, the last snake
    # segment is popped, meaning the snake is actually constantly created and recreated, rather than just
    # having positional data rewritten.
    snakeSegments.insert(0,list(snakePosition))
    if snakePosition[0] == raspberryPosition[0] and snakePosition[1] == raspberryPosition[1]:
        raspberrySpawned = 0
    else:
        snakeSegments.pop()

    # Spawn the raspberry in a random location if it has been eaten.    
    if raspberrySpawned == 0:
        x = random.randrange(1,32)
        y = random.randrange(1,24)
        raspberryPosition = [int(x*20),int(y*20)]
    raspberrySpawned = 1

    # Draw everything to screen
    playSurface.fill(black)
    for position in snakeSegments:
        pygame.draw.rect(playSurface,white,Rect(position[0], position[1], 20, 20))
    pygame.draw.rect(playSurface,red,Rect(raspberryPosition[0], raspberryPosition[1], 20, 20))
    pygame.display.flip()
    
    if snakePosition[0] > 620 or snakePosition[0] < 0:
        gameOver()
    if snakePosition[1] > 460 or snakePosition[1] < 0:
        for snakeBody in snakeSegments[1:]:
            if snakePosition[0] == snakeBody[0] and snakePosition[1] == snakeBody[1]:
                gameOver()
    fpsClock.tick(30)