User controlled sprite stuck in box. Python 2.7.9 w/Pygame - python-2.7

Question

Thanks for looking at my question and helping me out. I have a user controlled sprite that should cause the screen to shift around the sprite's position, kinda like an old Gameboy Pokemon game, yet that does not happen. Instead my sprite is stuck inside a box of coordinates that I used to help define parameters for background shift. This is the code I believe is causing this:
# Shift world left (-x)
if player.rect.right >= 510:
diff = player.rect.right - 510
player.rect.right = 510
current_level.shift_world_x(-diff)
# Shift world right (+x)
if player.rect.left <= 130:
diff = 130 - player.rect.left
player.rect.left = 130
current_level.shift_world_x(diff)
# Shift world up (-y)
if player.rect.top <= 100:
diff = 100 - player.rect.top
player.rect.top = 100
current_level.shift_world_y(diff)
# Shift world down (y)
if player.rect.bottom >= 380:
diff = player.rect.bottom - 380
player.rect.bottom = 380
current_level.shift_world_y(-diff)
If I put a # next to player.rect.right = 510, or any of the other three varients, my sprite can move freely, yet the screen will not shift.
Zip file with all assets is here:
https://www.dropbox.com/s/3g2w0mv1fuupetl/DoneGeon.zip?dl=0
The entirety of my code is as follows:
import pygame
"""---Global Constants---"""
# Colors
BLACK = (0, 0, 0)
# Screen Variables
screen_x = 720
screen_y = 480
# Background variables
back_x = 0
back_y = -243
back_x_change = 0
back_y_change = 0
class Player(pygame.sprite.Sprite):
"""---User Controled Character---"""
# Methods
def __init__(self):
"""---Contructor Function---"""
# Call parent's constructor
pygame.sprite.Sprite.__init__(self)
# Load player image
self.image = pygame.image.load("player.png").convert()
# Set referance to image "hit box"
self.rect = self.image.get_rect()
# Set speed of player
self.change_x = 0
self.change_y = 0
def update(self):
"""---Move the Player---"""
# Move left/right
self.rect.x += self.change_x
# Move up/down
self.rect.y += self.change_y
# User controlled movements
def go_left(self):
self.change_x = -3
def go_right(self):
self.change_x = 3
def go_up(self):
self.change_y = -3
def go_down(self):
self.change_y = 3
def stop_x(self):
self.change_x = 0
def stop_y(self):
self.change_y = 0
class Barrier(pygame.sprite.Sprite):
"""---Barriers that prevent player from passing---"""
def __init__(self,width,height):
""" Barrier constructor """
pygame.sprite.Sprite.__init__(self)
self.image = pygame.Surface([width,height])
self.image.fill(BLACK)
self.rect = self.image.get_rect()
class Level():
"""---All levels will spawn from this generic class---"""
def __init__(self,player):
""" Needed for when sprites collide with player """
self.barrier_list = pygame.sprite.Group()
self.enemy_list = pygame.sprite.Group()
self.player = player
# Distance world has been shifted left/right
self.world_shift_x = 0
# Background image
background_base = None
background_layera = None
# Distance world has been shifted up/down
self.world_shift_y = 0
def update(self):
""" Update everything on level """
self.barrier_list.update()
self.enemy_list.update()
def draw(self,screen):
""" Draw everything on level """
# Draw barriers
self.barrier_list.draw(screen)
# Draw the base layer
screen.blit(self.background_base,(back_x,back_y))
# Draw all sprites
self.enemy_list.draw(screen)
# Draw Layer A
screen.blit(self.background_layera,(back_x,back_y))
def shift_world_x(self,shift_x):
""" When character moves left/right, everything must follow """
# Track shift amount
self.world_shift_x += shift_x
# Go through all list and shift
for barrier in self.barrier_list:
barrier.rect.x += shift_x
for enemy in self.enemy_list:
enemy.rect.x += shift_x
def shift_world_y(self,shift_y):
""" When character moves up/down, everything must follow """
# Track shift amount
self.world_shift_y += shift_y
# Go through all list and shift
for barrier in self.barrier_list:
barrier.rect.y += shift_y
for enemy in self.enemy_list:
enemy.rect.y += shift_y
class Level_1(Level):
"""---Forest 1---"""
def __init__(self,player):
""" Create the level """
# Call parent constructor
Level.__init__(self,player)
self.level_limit_x = -1912
self.level_limit_y = 1080
# Make background
self.background_base = pygame.image.load("base1.png").convert()
self.background_layera = pygame.image.load("layera1.png").convert()
self.background_layera.set_colorkey(BLACK)
# List with w, h, x = 32, y = 32 of barriers
# Remove comment to activate-> level = []
# Go through the list above and add barriers
# Remove comment to activate-> for barriers in level:
def main():
"""---Main Program---"""
pygame.init()
# Set screen size and caption
size = (screen_x,screen_y)
screen = pygame.display.set_mode(size)
pygame.display.set_caption("DoneGeon")
# Create Player
player = Player()
# Create all levels
level_list= []
level_list.append(Level_1(player))
# Set current level
current_level_no = 0
current_level = level_list[current_level_no]
# Add all sprites
active_sprite_list = pygame.sprite.Group()
# Add player
player.level = current_level
player.rect.x = 360
player.rect.y = 240
active_sprite_list.add(player)
# Loop until closed
done = False
# Screen update rate
clock = pygame.time.Clock()
# -------- Main Program Loop -----------
while not done:
"""---Main event loop---"""
for event in pygame.event.get():
if event.type == pygame.QUIT:
done = True
"""---User Controls---"""
# Key Pressed
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.go_up()
if event.key == pygame.K_DOWN:
player.go_down()
# Key Released
if event.type == pygame.KEYUP:
if event.key == pygame.K_LEFT or event.key == pygame.K_RIGHT:
player.stop_x()
if event.key == pygame.K_UP or event.key == pygame.K_DOWN:
player.stop_y()
"""---Game Logic---"""
# Update Player
active_sprite_list.update()
# Update items in level
current_level.update()
# Shift world left (-x)
if player.rect.right >= 510:
diff = player.rect.right - 510
player.rect.right = 510
current_level.shift_world_x(-diff)
# Shift world right (+x)
if player.rect.left <= 130:
diff = 130 - player.rect.left
player.rect.left = 130
current_level.shift_world_x(diff)
# Shift world up (-y)
if player.rect.top <= 100:
diff = 100 - player.rect.top
player.rect.top = 100
current_level.shift_world_y(diff)
# Shift world down (y)
if player.rect.bottom >= 380:
diff = player.rect.bottom - 380
player.rect.bottom = 380
current_level.shift_world_y(-diff)
"""---Draw below here---"""
current_level.draw(screen)
active_sprite_list.draw(screen)
pygame.display.flip()
clock.tick(60)
pygame.quit()
if __name__ == "__main__":
main()
Thank you for any advice!

Answer 1

I think you'll find this easier to track down if you log the changes in player x and world x. Often with games small changes aren't visible so logging is the only way to monitor what's happening in the game loop.
I haven't tested this but my bet is that you've got a negative in the wrong place. This:
def shift_world_x(self,shift_x):
""" When character moves left/right, everything must follow """
suggests that if the player right edge moves past the world right edge the world right edge should extend to match the player but this code does the reverse:
if player.rect.right >= 510:
diff = player.rect.right - 510
player.rect.right = 510
current_level.shift_world_x(-diff)
If the player.right moves to 513 diff will be 3 so shift_world_x will be called with -3, moving the world box left to 507. Player right will then be set to 510 so the player right will still be outside the box the next loop. This suggests that the world image will drift to the left with the player sprite stuck at the right edge but it sounds like it's trapped against the right edge (I'm focussing on one edge because the logic is the same for all).
If you log player.rect.right and world.rect.right in the if shown above you should see the values as they change and get a better feel for what the game logic is doing.