"""
Simple snake example.
Sample Python/Pygame Programs
Simpson College Computer Science
http://programarcadegames.com/
http://simpson.edu/computer-science/
"""
import pygame
# --- Globals ---
# Colors
BLACK = (0, 0, 0)
WHITE = (255, 255, 255)
# Set the width and height of each snake segment
segment_width = 15
segment_height = 15
# Margin between each segment
segment_margin = 3
# Set initial speed
x_change = segment_width + segment_margin
y_change = 0
class Segment(pygame.sprite.Sprite):
	""" Class to represent one segment of the snake. """
	# -- Methods
	# Constructor function
	def __init__(self, x, y):
		# Call the parent's constructor
		super(pygame.sprite.Sprite,self).__init__()
		# Set height, width
		self.image = pygame.Surface([segment_width, segment_height])
		self.image.fill(WHITE)
		# Make our top-left corner the passed-in location.
		self.rect = self.image.get_rect()
		self.rect.x = x
		self.rect.y = y
# Call this function so the Pygame library can initialize itself
pygame.init()
# Create an 800x600 sized screen
screen = pygame.display.set_mode([800, 600])
# Set the title of the window
pygame.display.set_caption('Snake Example')
allspriteslist = pygame.sprite.Group()
# Create an initial snake
snake_segments = []
for i in range(15):
	x = 250 - (segment_width + segment_margin) * i
	y = 30
	segment = Segment(x, y)
	snake_segments.append(segment)
	allspriteslist.add(segment)
clock = pygame.time.Clock()
done = False
while not done:
	for event in pygame.event.get():
		if event.type == pygame.QUIT:
			done = True
	# Set the speed based on the key pressed
	# We want the speed to be enough that we move a full
	# segment, plus the margin.
	if event.type == pygame.KEYDOWN:
		if event.key == pygame.K_LEFT:
			x_change = (segment_width + segment_margin) * -1
			y_change = 0
		if event.key == pygame.K_RIGHT:
			x_change = (segment_width + segment_margin)
			y_change = 0
		if event.key == pygame.K_UP:
			x_change = 0
			y_change = (segment_height + segment_margin) * -1
		if event.key == pygame.K_DOWN:
			x_change = 0
			y_change = (segment_height + segment_margin)
	# Get rid of last segment of the snake
	# .pop() command removes last item in list
	old_segment = snake_segments.pop()
	allspriteslist.remove(old_segment)
	# Figure out where new segment will be
	x = snake_segments[0].rect.x + x_change
	y = snake_segments[0].rect.y + y_change
	segment = Segment(x, y)
	# Insert new segment into the list
	snake_segments.insert(0, segment)
	allspriteslist.add(segment)
	# -- Draw everything
	# Clear screen
	screen.fill(BLACK)
	allspriteslist.draw(screen)
	# Flip screen
	pygame.display.flip()
	# Pause
	clock.tick(5)
pygame.quit()
