alien_invasion.py

import sys
from time import sleep

import pygame 

from settings import Settings 
from game_stats import GameStats
from scoreboard import Scoreboard
from button import Button
from ship import Ship
from bullet import Bullet
from alien import Alien

class AlienInvasion:
    """Overall class to manage game assets and behavior"""

    def __init__(self):
        """Initialize the game, and create game resources"""
        
        pygame.init()
        self.clock = pygame.time.Clock()
        
        self.settings = Settings()
        self.screen = pygame.display.set_mode((0,0), pygame.FULLSCREEN)
        self.settings.screen_width = self.screen.get_rect().width
        self.settings.screen_height = self.screen.get_rect().height
        
        pygame.display.set_caption("alien invasion")
        # create an instance to store game stats and create scoreboard 
        self.stats = GameStats(self)
        self.sb = Scoreboard(self)
        self.ship = Ship(self)
        self.bullets = pygame.sprite.Group()
        self.aliens = pygame.sprite.Group()

        self._create_fleet()

        # start alien invasion in an active state
        self.game_active = False 

        # make the play button
        self.play_button = Button(self, "Play")
       

    def run_game(self):
        """start the main loop for the game"""
        while True:
            self._check_events()

            if self.game_active :
                self.ship.update()
                self._update_bullets()
                self._update_aliens()
            
            self._update_screen() 
            self.clock.tick(60)
            
           
            # watch for keyboard and mouse events
    def _check_events(self):
        """respond to keypresses and mouse events"""
        for event in pygame.event.get():
            if event.type == pygame.QUIT : 
                sys.exit()
            elif event.type == pygame.KEYDOWN:
                self._check_keydown_events(event)
            elif event.type == pygame.KEYUP:
                self._check_keyup_events(event)
            elif event.type == pygame.MOUSEBUTTONDOWN:
                mouse_pos = pygame.mouse.get_pos()
                self._check_play_button(mouse_pos)

    def _check_play_button(self, mouse_pos):
        """start a new gamme when the player clicks play"""
        button_clicked = self.play_button.rect.collidepoint(mouse_pos)
        if button_clicked and not self.game_active :

            # Reset the game statistics
            self.stats.reset_stats()
            self.game_active = True

            # Prepare the scoreboard images
            self.sb.prep_score()
            self.sb.prep_level()
            self.sb.prep_high_score()
            self.sb.prep_ships()

            # get rid of remaining bullets and aliens
            self.bullets.empty()
            self.aliens.empty()

            # create new fleet and center ship
            self._create_fleet()
            self.ship.center_ship()

            # hide the mouse cursor 
            pygame.mouse.set_visible(False)

    def _check_keydown_events(self, event):
        """respond to keypresses"""
        if event.key == pygame.K_RIGHT:
            self.ship.moving_right = True
        elif event.key == pygame.K_LEFT:
            self.ship.moving_left = True
        elif event.key == pygame.K_q :
            sys.exit()
        elif event.key == pygame.K_SPACE:
            self._fire_bullet()

    def _check_keyup_events(self, event):
        """respond to key releases"""
        if event.key == pygame.K_RIGHT:
            self.ship.moving_right = False
        elif event.key == pygame.K_LEFT:
            self.ship.moving_left = False

    def _fire_bullet(self):
        """ create a new bullet and add it to the bullet group"""
        if len(self.bullets) < self.settings.bullets_allowed:
            new_bullet = Bullet(self)
            self.bullets.add(new_bullet)

    def _create_fleet(self):
        """create the fleet of aliens"""
        # create an alien and keep adding aliens until there's no room left
        # spacing between aliens is one alien width and one alien height
        alien = Alien(self)
        alien_width, alien_height  = alien.rect.size
        current_x, current_y = alien_width, alien_height
        while current_y < (self.settings.screen_height - 9* alien_height):
            while current_x < (self.settings.screen_width - 2* alien_width) :
                self._create_alien(current_x, current_y)
                current_x += 2 * alien_width

            # finished a row, reset x value and increment y value
            current_x = alien_width
            current_y += 2 * alien_height

    def _create_alien(self, x_position, y_position):
        """create an alien and place it in the fleet"""
        new_alien = Alien(self)
        new_alien.x = x_position
        new_alien.rect.x = x_position
        new_alien.rect.y = y_position
        self.aliens.add(new_alien)

    def _update_aliens(self):
        """check if the fleet is at an edge, then update positions"""
        self._check_fleet_edges()
        self.aliens.update()
        
        # look for alien-ship collisions
        if pygame.sprite.spritecollideany(self.ship, self.aliens):
            self._ship_hit()
            print("ship hit!")

        # look for aliens hitting the bottom of the screen
        self._check_aliens_bottom()

    def _check_aliens_bottom(self):
        """check if alien has reached bottom of the screen"""
        for alien in self.aliens.sprites():
            if alien.rect.bottom >= self.settings.screen_height:
                #treat this the same as if ship got hit 
                self._ship_hit()
                break

    def _update_bullets(self):
        """update position of bullets and get rid of the old bullets"""
        # update bullet positions
        self.bullets.update()

        #  get rid of bullets that have disappeared 
        for bullet in self.bullets.copy():
            if bullet.rect.bottom <= 0:
                self.bullets.remove(bullet)
        print(len(self.bullets))

        self._check_bullet_alien_collision()

    def _check_bullet_alien_collision(self):    
        """respond to bullet-alien collisions"""
        # remove any bullets and aliens that have collided
        collisions = pygame.sprite.groupcollide(self.bullets, self.aliens, True, True)
        if collisions:
            for aliens in collisions.values():
                self.stats.score += self.settings.alien_points * len(aliens)
        self.sb.prep_score()
        self.sb.check_high_score()

        if not self.aliens:
            # destroy existing bullets and create new fleet
            self.bullets.empty()
            self._create_fleet()

            # increase level and update scoreboard
            self.stats.level += 1
            self.sb.prep_level()

    def _update_screen(self):
        """update images on screen and flip to the new screen"""
         # redraw the screen during each pass through the loop
        self.screen.fill(self.settings.bg_color)
        for bullet in self.bullets.sprites():
            bullet.draw_bullet()
        self.ship.blitme()
        self.aliens.draw(self.screen)

        # draw the score infromation
        self.sb.show_score()

        # draw the play button if the game is inactive
        if not self.game_active:
            self.play_button.draw_button()
            
        # MAKE THE MOST RECENTLY DRAWN SCREEN VISIBLE
        pygame.display.flip()

    def _check_fleet_edges(self):
        """respond appropriately if any aliens have reached an edge"""
        for alien in self.aliens.sprites():
            if alien.check_edges():
                self._change_fleet_direction()
                break

    def _change_fleet_direction(self):
        """drop the entire fleet and change the fleet's direction"""
        for alien in self.aliens.sprites():
            alien.rect.y += self.settings.fleet_drop_speed
        self.settings.fleet_direction *= -1 

    def _ship_hit(self):
        """respond to the ship being hit by an alien"""
        if self.stats.ships_left > 0:
            # decrement ship_left, update scoreboard 
            self.stats.ships_left -= 1
            self.sb.prep_ships()
            # get rid of any remaining bullets and aliens 
            self.bullets.empty()
            self.aliens.empty()
            # create a new fleet and centre the ship
            self._create_fleet()
            self.ship.center_ship()
            # pause 
            sleep(0.5)
        else:
            self.game_active = False
            pygame.mouse.set_visible(True)
            

if __name__ == '__main__' :
    # make a game instance and run the game 
    ai = AlienInvasion()
    ai.run_game()