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

From:

Explanation video: http://youtu.be/BCxWJgN4Nnc

Part of a series:
"""

import pygame

# Global constants

# Colors
BLACK = (0, 0, 0)
WHITE = (255, 255, 255)
GREEN = (0, 255, 0)
RED = (255, 0, 0)
BLUE = (0, 0, 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. """

# -- Methods
def __init__(self):
""" Constructor function """

# Call the parent's constructor
super().__init__()

# Create an image of the block, and fill it with a color.
# This could also be an image loaded from the disk.
width = 40
height = 60
self.image = pygame.Surface([width, height])
self.image.fill(RED)

# Set a referance to the image rect.
self.rect = self.image.get_rect()

# Set speed vector of player
self.change_x = 0
self.change_y = 0

# List of sprites we can bump against
self.level = None

def update(self):
""" Move the player. """
# Gravity
self.calc_grav()

# Move left/right
self.rect.x += self.change_x

# See if we hit anything
block_hit_list = pygame.sprite.spritecollide(self, self.level.platform_list, 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
elif self.change_x < 0:
# 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.level.platform_list, 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
elif self.change_y < 0:
self.rect.top = block.rect.bottom

# Stop our vertical movement
self.change_y = 0

def calc_grav(self):
""" Calculate effect of gravity. """
if self.change_y == 0:
self.change_y = 1
else:
self.change_y += .35

# See if we are on the ground.
if self.rect.y >= SCREEN_HEIGHT - self.rect.height and self.change_y >= 0:
self.change_y = 0
self.rect.y = SCREEN_HEIGHT - self.rect.height

def jump(self):
""" Called when user hits 'jump' button. """

# move down a bit and see if there is a platform below us.
# Move down 2 pixels because it doesn't work well if we only move down
# 1 when working with a platform moving down.
self.rect.y += 2
platform_hit_list = pygame.sprite.spritecollide(self, self.level.platform_list, False)
self.rect.y -= 2

# If it is ok to jump, set our speed upwards
if len(platform_hit_list) > 0 or self.rect.bottom >= SCREEN_HEIGHT:
self.change_y = -10

# Player-controlled movement:
def go_left(self):
""" Called when the user hits the left arrow. """
self.change_x = -6

def go_right(self):
""" Called when the user hits the right arrow. """
self.change_x = 6

def stop(self):
""" Called when the user lets off the keyboard. """
self.change_x = 0

class Platform(pygame.sprite.Sprite):
""" Platform the user can jump on """

def __init__(self, width, height):
""" Platform constructor. Assumes constructed with user passing in
an array of 5 numbers like what's defined at the top of this
code. """
super().__init__()

self.image = pygame.Surface([width, height])
self.image.fill(GREEN)

self.rect = self.image.get_rect()

class Level(object):
""" This is a generic super-class used to define a level.
Create a child class for each level with level-specific
info. """

def __init__(self, player):
""" Constructor. Pass in a handle to player. Needed for when moving platforms
collide with the player. """
self.platform_list = pygame.sprite.Group()
self.enemy_list = pygame.sprite.Group()
self.player = player

# Background image
self.background = None

# Update everythign on this level
def update(self):
""" Update everything in this level."""
self.platform_list.update()
self.enemy_list.update()

def draw(self, screen):
""" Draw everything on this level. """

# Draw the background
screen.fill(BLUE)

# Draw all the sprite lists that we have
self.platform_list.draw(screen)
self.enemy_list.draw(screen)

# Create platforms for the level
class Level_01(Level):
""" Definition for level 1. """

def __init__(self, player):
""" Create level 1. """

# Call the parent constructor
Level.__init__(self, player)

# Array with width, height, x, and y of platform
level = [[210, 70, 500, 500],
[210, 70, 200, 400],
[210, 70, 600, 300],
]

# Go through the array above and add platforms
for platform in level:
block = Platform(platform[0], platform[1])
block.rect.x = platform[2]
block.rect.y = platform[3]
block.player = self.player

def main():
""" Main Program """
pygame.init()

# Set the height and width of the screen
size = [SCREEN_WIDTH, SCREEN_HEIGHT]
screen = pygame.display.set_mode(size)

pygame.display.set_caption("Platformer Jumper")

# Create the player
player = Player()

# Create all the levels
level_list = []
level_list.append( Level_01(player) )

# Set the current level
current_level_no = 0
current_level = level_list[current_level_no]

active_sprite_list = pygame.sprite.Group()
player.level = current_level

player.rect.x = 340
player.rect.y = SCREEN_HEIGHT - player.rect.height

# Loop until the user clicks the close button.
done = False

# Used to manage how fast the screen updates
clock = pygame.time.Clock()

# -------- Main Program Loop -----------
while not done:
for event in pygame.event.get():
if event.type == pygame.QUIT:
done = True

if event.type == pygame.KEYDOWN:
if event.key == pygame.K_LEFT:
player.go_left()
if event.key == pygame.K_RIGHT:
player.go_right()
if event.key == pygame.K_UP:
player.jump()

if event.type == pygame.KEYUP:
if event.key == pygame.K_LEFT and player.change_x < 0:
player.stop()
if event.key == pygame.K_RIGHT and player.change_x > 0:
player.stop()

# Update the player.
active_sprite_list.update()

# Update items in the level
current_level.update()

# If the player gets near the right side, shift the world left (-x)
if player.rect.right > SCREEN_WIDTH:
player.rect.right = SCREEN_WIDTH

# If the player gets near the left side, shift the world right (+x)
if player.rect.left < 0:
player.rect.left = 0

# ALL CODE TO DRAW SHOULD GO BELOW THIS COMMENT
current_level.draw(screen)
active_sprite_list.draw(screen)

# ALL CODE TO DRAW SHOULD GO ABOVE THIS COMMENT

# Limit to 60 frames per second
clock.tick(60)

# Go ahead and update the screen with what we've drawn.
pygame.display.flip()

# Be IDLE friendly. If you forget this line, the program will 'hang'
# on exit.
pygame.quit()

if __name__ == "__main__":
main()

```
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