第五部分4

game_functions.py

@@ -152,3 +152,52 @@ def change_fleet_direction(ai_settings, aliens):
         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)
+