Finished Chapter 13 source code programming

src/project_i_alien_invasion/alien.py

@@ -0,0 +1,36 @@
+import pygame
+from pygame.sprite import Sprite
+
+class Alien(Sprite):
+    """A class to represent a single alien in the fleet"""
+
+    def __init__(self, ai_game):
+        """initialize the alien and set its starting position"""
+        super().__init__()
+        self.screen = ai_game.screen
+        self.settings = ai_game.settings
+
+        # Load the alien image and set its rect attribute
+        self.image = pygame.image.load('alien.bmp')
+        self.rect = self.image.get_rect()
+
+        # Start each new alien near the top left of the screen
+        # Add a space to the left of alien (which equals to the alien's width)
+        self.rect.x = self.rect.width
+        self.rect.y = self.rect.height
+
+        # Store the alien's exact horizontal position
+        self.x = float(self.rect.x)
+
+    def check_edges(self):
+        """Return True if alien is at edge of screen"""
+        screen_rect = self.screen.get_rect()
+        if self.rect.right >= screen_rect.right or self.rect.left <= 0:
+            return True
+        else:
+            return False
+
+    def update(self):
+        """Move the alien to the right"""
+        self.x += self.settings.alien_speed * self.settings.fleet_direction
+        self.rect.x = self.x # track the alien's exact position with self.x attribute.

src/project_i_alien_invasion/alien_invasion.py

@@ -1,8 +1,14 @@
 import sys
+from time import sleep
+
 import pygame
+
 from settings import Settings
+from game_stats import GameStats
 from ship import Ship
 from bullet import Bullet
+from alien import Alien
+
 
 class AlienInvasion:
     """Overall class to manage game assets and behaviour"""
@@ -20,16 +26,25 @@ class AlienInvasion:
         self.settings.screen_height = self.screen.get_rect().height
         pygame.display.set_caption("Alien Invasion")
 
+        # Create an instance to store game statistics
+        self.stats = GameStats(self)
+
         self.ship = Ship(self)
         self.bullets = pygame.sprite.Group() # 
+        self.aliens = pygame.sprite.Group()
+
+        self._create_fleet()
 
     def run_game(self):
         """Start the main loop for the game"""
         while True:
 
             self._check_events()
+
+            if self.stats.game_active:
                 self.ship.update()
                 self._update_bullets()
+                self._update_aliens()
 
             self._update_screen()
 
@@ -77,6 +92,42 @@ class AlienInvasion:
             if bullet.rect.bottom <= 0:
                 self.bullets.remove(bullet)
         print(len(self.bullets))
+        self._check_bullet_alien_collisions()
+    
+    def _check_bullet_alien_collisions(self):
+        """Respond to the bullet-alien collisions"""
+        # Check for any bullets that have hit aliens.
+        #  If so, get rid of the bullet and the alien
+        collisions = pygame.sprite.groupcollide(self.bullets, self.aliens, True, True)
+
+        # If alien fleet is destroyed, repopulate another one
+        if not self.aliens:
+            self.bullets.empty()
+            self._create_fleet()
+
+    def _check_aliens_bottom(self):
+        """Check if any aliens have reached the bottom of screen"""
+        screen_rect = self.screen.get_rect()
+        for alien in self.aliens.sprites():
+            if alien.rect.bottom >= screen_rect.bottom:
+                # 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,
+        Update the positions of all aliens in the fleet
+        """
+        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 _update_screen(self):
         """Update images on the screen, and flip to the new screen"""
@@ -84,9 +135,75 @@ class AlienInvasion:
         self.ship.blitme()
         for bullet in self.bullets.sprites():
             bullet.draw_bullet()
+        self.aliens.draw(self.screen)
 
         pygame.display.flip()
 
+    def _create_fleet(self):
+        """
+        Create the fleet of aliens.
+        """
+        # Create an alien and find the number of alines in a row
+        # Spacing between each alien is equal to one alien width.
+        alien = Alien(self)
+        alien_width, alien_height = alien.rect.size
+        availalbe_space_x = self.settings.screen_width - (2 * alien_width)
+        number_aliens_x = availalbe_space_x // (2 * alien_width)
+
+        # Determine the number of rows of aliens that fit on the screen
+        ship_height = self.ship.rect.height
+        availalbe_space_y = (self.settings.screen_height - (3 * alien_height) - ship_height)
+        number_rows = availalbe_space_y // (2 * alien_height)
+
+        # Create the full fleet of aliens
+        for row_number in range(number_rows):
+            for alien_number in range(number_aliens_x):
+                # Create an alien and place it in the row
+                self._create_alien(alien_number, row_number)
+
+    def _create_alien(self, alien_number, row_number):
+        """Create an alien and place it in the row in correct place"""
+        alien = Alien(self)
+        alien_width, alein_height = alien.rect.size
+        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
+        self.aliens.add(alien)
+
+    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 _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 # Break out of the loop if an alien is at edge
+
+    def _ship_hit(self):
+        """Respond to the ship being hit by an alien"""
+
+        if self.stats.ships_left > 0:
+            # Decrement ships_left
+            self.stats.ships_left -= 1
+
+            # Get rid of any remaining aliens and bullets
+            self.aliens.empty()
+            self.bullets.empty()
+
+            # Create a new fleet and center the ship
+            self._create_fleet()
+            self.ship.center_ship()
+
+            # Pause
+            sleep(0.5)
+        else:
+            self.stats.game_active = False
+
 if __name__ == '__main__':
     ai = AlienInvasion()
     ai.run_game()

src/project_i_alien_invasion/game_stats.py

@@ -0,0 +1,14 @@
+class GameStats:
+    """Track statistics for Alien Invasion"""
+
+    def __init__(self, ai_game):
+        """Initialize statistics"""
+        self.settings = ai_game.settings
+        self.reset_stats()
+
+        # Start Alien Invasion in an active state
+        self.game_active = True
+
+    def reset_stats(self):
+        """Initialize statics that can change during the game"""
+        self.ships_left = self.settings.ship_limit

src/project_i_alien_invasion/settings.py

@@ -11,10 +11,18 @@ class Settings:
         
         # Ship settings
         self.ship_speed = 1.5
+        self.ship_limit = 3
 
         # Bullet settings
-        self.bullet_speed = 1.0
+        self.bullet_speed = 1.5
         self.bullet_width = 3
         self.bullet_height = 15
         self.bullet_color = (60,60,60)
         self.bullets_allowed = 3
+
+        # Alien settings
+        self.alien_speed = 1.0
+        self.fleet_drop_speed = 10
+        # fleet_direction of 1 represents right; -1 represent left
+        self.fleet_direction = 1
+

src/project_i_alien_invasion/ship.py

@@ -34,3 +34,8 @@ class Ship:
     def blitme(self):
         """Draw the ship at its current location"""
         self.screen.blit(self.image,self.rect)
+
+    def center_ship(self):
+        """Center the ship on the screen"""
+        self.rect.midbottom = self.screen_rect.midbottom
+        self.x = float(self.rect.x)