```"""
Sample Python/Pygame Programs
Simpson College Computer Science
http://simpson.edu/computer-science/

From:

Explanation video: http://youtu.be/8IRyt7ft7zg

Part of a series:
"""

import pygame

# -- Global constants

# Colors
BLACK = (0, 0, 0)
WHITE = (255, 255, 255)
BLUE = (50, 50, 255)

# Screen dimensions
SCREEN_WIDTH = 800
SCREEN_HEIGHT = 600

class Player(pygame.sprite.Sprite):
""" This class represents the bar at the bottom that the player
controls. """

# Constructor function
def __init__(self, x, y):
# Call the parent's constructor
super().__init__()

# Set height, width
self.image = pygame.Surface([15, 15])
self.image.fill(WHITE)

# Make our top-left corner the passed-in location.
self.rect = self.image.get_rect()
self.rect.y = y
self.rect.x = x

# Set speed vector
self.change_x = 0
self.change_y = 0
self.walls = None

def changespeed(self, x, y):
""" Change the speed of the player. """
self.change_x += x
self.change_y += y

def update(self):
""" Update the player position. """
# Move left/right
self.rect.x += self.change_x

# Did this update cause us to hit a wall?
block_hit_list = pygame.sprite.spritecollide(self, self.walls, False)
for block in block_hit_list:
# If we are moving right, set our right side to the left side of
# the item we hit
if self.change_x > 0:
self.rect.right = block.rect.left
else:
# Otherwise if we are moving left, do the opposite.
self.rect.left = block.rect.right

# Move up/down
self.rect.y += self.change_y

# Check and see if we hit anything
block_hit_list = pygame.sprite.spritecollide(self, self.walls, False)
for block in block_hit_list:

# Reset our position based on the top/bottom of the object.
if self.change_y > 0:
self.rect.bottom = block.rect.top
else:
self.rect.top = block.rect.bottom

class Wall(pygame.sprite.Sprite):
""" Wall the player can run into. """
def __init__(self, x, y, width, height):
""" Constructor for the wall that the player can run into. """
# Call the parent's constructor
super().__init__()

# Make a blue wall, of the size specified in the parameters
self.image = pygame.Surface([width, height])
self.image.fill(BLUE)

# Make our top-left corner the passed-in location.
self.rect = self.image.get_rect()
self.rect.y = y
self.rect.x = x

# Call this function so the Pygame library can initialize itself
pygame.init()

# Create an 800x600 sized screen
screen = pygame.display.set_mode([SCREEN_WIDTH, SCREEN_HEIGHT])

# Set the title of the window
pygame.display.set_caption('Test')

# List to hold all the sprites
all_sprite_list = pygame.sprite.Group()

# Make the walls. (x_pos, y_pos, width, height)
wall_list = pygame.sprite.Group()

wall = Wall(0, 0, 10, 600)

wall = Wall(10, 0, 790, 10)

wall = Wall(10, 200, 100, 10)

# Create the player paddle object
player = Player(50, 50)
player.walls = wall_list

clock = pygame.time.Clock()

done = False

while not done:

for event in pygame.event.get():
if event.type == pygame.QUIT:
done = True

elif event.type == pygame.KEYDOWN:
if event.key == pygame.K_LEFT:
player.changespeed(-3, 0)
elif event.key == pygame.K_RIGHT:
player.changespeed(3, 0)
elif event.key == pygame.K_UP:
player.changespeed(0, -3)
elif event.key == pygame.K_DOWN:
player.changespeed(0, 3)

elif event.type == pygame.KEYUP:
if event.key == pygame.K_LEFT:
player.changespeed(3, 0)
elif event.key == pygame.K_RIGHT:
player.changespeed(-3, 0)
elif event.key == pygame.K_UP:
player.changespeed(0, 3)
elif event.key == pygame.K_DOWN:
player.changespeed(0, -3)

all_sprite_list.update()

screen.fill(BLACK)

all_sprite_list.draw(screen)

pygame.display.flip()

clock.tick(60)

pygame.quit()

```
﻿