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() # To handle framerate.
        self.settings = Settings()

        self.screen = pygame.display.set_mode(
            (self.settings.screen_width, self.settings.screen_height))
        pygame.display.set_caption("Alien Invasion")

        # Create an instance to store game statistics 
        # and create a 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()

        # Set the background color.
        self.bg_color = (230, 230, 230)

        # Start Alien Invasion in an inactive 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()

            # Only update game elements when game is active.
            if self.game_active:
                self.ship.update()
                self._update_bullets()
                self._update_aliens()

            self._update_screen()
            self.clock.tick(60) # hold fram rate at 60 fps

    def _update_bullets(self):
        """Update position of bullets and get rid of 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)
        self._check_bullet_alien_collissions()
    
    def _check_bullet_alien_collissions(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 a new fleet.
            self.bullets.empty()
            self._create_fleet()
            self.settings.increase_speed()

            # Increase level.
            self.stats.level += 1
            self.sb.prep_level()
    
    def _ship_hit(self):
        """Respond to the ship being hit by an alien."""
        if self.stats.ships_left > 0:
            # Decrement ships left, and update scoreboard.
            self.stats.ships_left -= 1
            self.sb.prep_ships()

            # Get rid of any bullets and aliens.
            self.bullets.empty()
            self.aliens.empty()

            # Create a new fleet and center the ship.
            self._create_fleet()
            self.ship.center_ship()

            # Pause.
            sleep(0.5) 
        else:
            self.game_active = False
            pygame.mouse.set_visible(True)
    
    def _check_aliens_bottom(self):
        """Check if any aliens have reached the bottom of the screen."""
        for alien in self.aliens.sprites():
            if alien.rect.bottom >= self.settings.screen_height:
                # Treat this the same as if the ship got hit.
                self._ship_hit()
                break
    
    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()
        
        # Look for aliens hitting the bottom of the screen.
        self._check_aliens_bottom()

    def _create_fleet(self):
        """Create the fleet of aliens."""
        # Create an alien and keep adding aliens until 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 - 3 * 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 _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 _update_screen(self):
        # Update images on the screen, and flip to the new screen.
        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 information.
        self.sb.show_score()

        # Draw the play button if the game is inactive.
        if not self.game_active:
            self.play_button.draw_button()

        pygame.display.flip() # "Flip" the page
            

    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 game when the player clicks play."""
        button_clicked = self.play_button.rect.collidepoint(mouse_pos)
        if button_clicked and not self.game_active:
            if self.play_button.rect.collidepoint(mouse_pos):
                # Reset game settings.
                self.settings.initialize_dynamic_settings()
                self.stats.reset_stats()
                self.sb.prep_score()
                self.sb.prep_level()
                self.sb.prep_ships()
                self.game_active = True

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

                # Create a new fleet and center the 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 key presses."""
        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 bullets group."""
        if len(self.bullets) < self.settings.bullets_allowed:
            new_bullet = Bullet(self)
            self.bullets.add(new_bullet)            

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