game_functions.py

import sys

from time import sleep

import pygame

from bullet import Bullet

from alien import Alien

def check_keydown_events(event, ai_settings, screen, ship, bullets):

" " " Respond to keypresses. " " "

if event. key == pygame. K_RIGHT:

ship. moving_right = True

elifevent. key == pygame. K_LEFT:

ship. moving_left = True

elifevent. key == pygame. K_SPACE:

fire_bullet(ai_settings, screen, ship, bullets)

elifevent. key == pygame. K_q:

sys. exit()

def check_keyup_events(event, ship):

" " " Respond to key releases. " " "

if event. key == pygame. K_RIGHT:

ship. moving_right = False

elifevent. key == pygame. K_LEFT:

ship. moving_left = False

def check_events(ai_settings, screen, stats, sb, play_button, ship, aliens,

bullets):

" " " Respond to keypresses and mouse events. " " "

for event in pygame. event. get():

if event. type == pygame. QUIT:

sys. exit()

elifevent. type == pygame. KEYDOWN:

check_keydown_events(event, ai_settings, screen, ship, bullets)

elifevent. type == pygame. KEYUP:

check_keyup_events(event, ship)

elifevent. type == pygame. MOUSEBUTTONDOWN:

mouse_x, mouse_y = pygame. mouse. get_pos()

check_play_button(ai_settings, screen, stats, sb, play_button,

ship, aliens, bullets, mouse_x, mouse_y)

def check_play_button(ai_settings, screen, stats, sb, play_button, ship,

aliens, bullets, mouse_x, mouse_y):

" " " Start a new game when the player clicks Play. " " "

button_clicked = play_button. rect. collidepoint(mouse_x, mouse_y)

if button_clicked and not stats. game_active:

# Reset the game settings.

ai_settings. initialize_dynamic_settings()

# Hide the mouse cursor.

pygame. mouse. set_visible(False)

# Reset the game statistics.

stats. reset_stats()

stats. game_active = True

# Reset the scoreboard images.

sb. prep_score()

sb. prep_high_score()

sb. prep_level()

sb. prep_ships()

# Empty the list of aliens and bullets.

aliens. empty()

bullets. empty()

# Create a new fleet and center the ship.

create_fleet(ai_settings, screen, ship, aliens)

ship. center_ship()

def fire_bullet(ai_settings, screen, ship, bullets):

" " " Fire a bullet, if limit not reached yet. " " "

# Create a new bullet, add to bullets group.

if len(bullets) < ai_settings. bullets_allowed:

new_bullet = Bullet(ai_settings, screen, ship)

bullets. add(new_bullet)

def update_screen(ai_settings, screen, stats, sb, ship, aliens, bullets,

play_button):

" " " Update images on the screen, and flip to the new screen. " " "

# Redraw the screen, each pass through the loop.

screen. fill(ai_settings. bg_color)

# Redraw all bullets, behind ship and aliens.

for bullet in bullets. sprites():

bullet. draw_bullet()

ship. blitme()

aliens. draw(screen)

# Draw the score information.

sb. show_score()

# Draw the play button if the game is inactive.

if not stats. game_active:

play_button. draw_button()

# Make the most recently drawn screen visible.

pygame. display. flip()

def update_bullets(ai_settings, screen, stats, sb, ship, aliens, bullets):

" " " Update position of bullets, and get rid of old bullets. " " "

# Update bullet positions.

bullets. update()

# Get rid of bullets that have disappeared.

for bullet in bullets. copy():

if bullet. rect. bottom< = 0:

bullets. remove(bullet)

check_bullet_alien_collisions(ai_settings, screen, stats, sb, ship,

aliens, bullets)

def check_high_score(stats, sb):

" " " Check to see if there's a new high score. " " "

if stats. score> stats. high_score:

stats. high_score = stats. score

sb. prep_high_score()

def check_bullet_alien_collisions(ai_settings, screen, stats, sb, ship,

aliens, bullets):

" " " Respond to bullet-alien collisions. " " "

# Remove any bullets and aliens that have collided.

collisions = pygame. sprite. groupcollide(bullets, aliens, True, True)

if collisions:

for aliens in collisions. values():

stats. score += ai_settings. alien_points * len(aliens)

sb. prep_score()

check_high_score(stats, sb)

if len(aliens) == 0:

# If the entire fleet is destroyed, start a new level.

bullets. empty()

ai_settings. increase_speed()

# Increase level.

stats. level += 1

sb. prep_level()

create_fleet(ai_settings, screen, ship, aliens)

def check_fleet_edges(ai_settings, aliens):

" " " Respond appropriately if any aliens have reached an edge. " " "

for alien in aliens. sprites():

if alien. check_edges():

change_fleet_direction(ai_settings, aliens)

break

def change_fleet_direction(ai_settings, aliens):

" " " Drop the entire fleet, and change the fleet's direction. " " "

for alien in aliens. sprites():

alien. rect. y += ai_settings. fleet_drop_speed

ai_settings. fleet_direction *= -1

def ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets):

" " " Respond to ship being hit by alien. " " "

if stats. ships_left> 0:

# Decrement ships_left.

stats. ships_left -= 1

# Update scoreboard.

sb. prep_ships()

else:

stats. game_active = False

pygame. mouse. set_visible(True)

# Empty the list of aliens and bullets.

aliens. empty()

bullets. empty()

# Create a new fleet, and center the ship.

create_fleet(ai_settings, screen, ship, aliens)

ship. center_ship()

# Pause.

sleep(0. 5)

def check_aliens_bottom(ai_settings, screen, stats, sb, ship, aliens,

bullets):

" " " Check if any aliens have reached the bottom of the screen. " " "

screen_rect = screen. get_rect()

for alien in aliens. sprites():

if alien. rect. bottom> = screen_rect. bottom:

# Treat this the same as if the ship got hit.

ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets)

break

def update_aliens(ai_settings, screen, stats, sb, ship, aliens, bullets):

" " "

Check if the fleet is at an edge,

then update the postions of all aliens in the fleet.

" " "

check_fleet_edges(ai_settings, aliens)

aliens. update()

# Look for alien-ship collisions.

if pygame. sprite. spritecollideany(ship, aliens):

ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets)

# Look for aliens hitting the bottom of the screen.

check_aliens_bottom(ai_settings, screen, stats, sb, ship, aliens, bullets)

def get_number_aliens_x(ai_settings, alien_width):

" " " Determine the number of aliens that fit in a row. " " "

available_space_x = ai_settings. screen_width - 2 * alien_width

number_aliens_x = int(available_space_x / (2 * alien_width))

return number_aliens_x

def get_number_rows(ai_settings, ship_height, alien_height):

" " " Determine the number of rows of aliens that fit on the screen. " " "

available_space_y = (ai_settings. screen_height -

(3 * alien_height) - ship_height)

number_rows = int(available_space_y / (2 * alien_height))

return number_rows

def create_alien(ai_settings, screen, aliens, alien_number, row_number):

" " " Create an alien, and place it in the row. " " "

alien = Alien(ai_settings, screen)

alien_width = alien. rect. width

alien. x = alien_width + 2 * alien_width * alien_number

alien. rect. x = alien. x

alien. rect. y = alien. rect. height + 2 * alien. rect. height * row_number

aliens. add(alien)

def create_fleet(ai_settings, screen, ship, aliens):

" " " Create a full fleet of aliens. " " "

# Create an alien, and find number of aliens in a row.

alien = Alien(ai_settings, screen)

number_aliens_x = get_number_aliens_x(ai_settings, alien. rect. width)

number_rows = get_number_rows(ai_settings, ship. rect. height,

alien. rect. height)

# Create the fleet of aliens.

for row_number in range(number_rows):

for alien_number in range(number_aliens_x):

create_alien(ai_settings, screen, aliens, alien_number,

row_number)

****************************************************************************