diff --git a/game_functions.py b/game_functions.py
new file mode 100644
index 0000000..638e1ca
--- /dev/null
+++ b/game_functions.py
@@ -0,0 +1,256 @@
+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
+    elif event.key == pygame.K_LEFT:
+        ship.moving_left = True
+    elif event.key == pygame.K_SPACE:
+        fire_bullet(ai_settings, screen, ship, bullets)
+    elif event.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
+    elif event.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()
+        elif event.type == pygame.KEYDOWN:
+            check_keydown_events(event, ai_settings, screen, ship, bullets)
+        elif event.type == pygame.KEYUP:
+            check_keyup_events(event, ship)
+        elif event.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)
\ No newline at end of file
diff --git a/game_stats.py b/game_stats.py
new file mode 100644
index 0000000..c7969a5
--- /dev/null
+++ b/game_stats.py
@@ -0,0 +1,19 @@
+class GameStats():
+    """Track statistics for Alien Invasion."""
+
+    def __init__(self, ai_settings):
+        """Initialize statistics."""
+        self.ai_settings = ai_settings
+        self.reset_stats()
+
+        # Start game in an inactive state.
+        self.game_active = False
+
+        # High score should never be reset.
+        self.high_score = 0
+
+    def reset_stats(self):
+        """Initialize statistics that can change during the game."""
+        self.ships_left = self.ai_settings.ship_limit
+        self.score = 0
+        self.level = 1
\ No newline at end of file
diff --git a/main.py b/main.py
new file mode 100644
index 0000000..d3f5a12
--- /dev/null
+++ b/main.py
@@ -0,0 +1 @@
+
diff --git a/scoreboard.py b/scoreboard.py
new file mode 100644
index 0000000..d48c09b
--- /dev/null
+++ b/scoreboard.py
@@ -0,0 +1,76 @@
+import pygame.font
+from pygame.sprite import Group
+
+from ship import Ship
+
+
+class Scoreboard():
+    """A class to report scoring information."""
+
+    def __init__(self, ai_settings, screen, stats):
+        """Initialize scorekeeping attributes."""
+        self.screen = screen
+        self.screen_rect = screen.get_rect()
+        self.ai_settings = ai_settings
+        self.stats = stats
+
+        # Font settings for scoring information.
+        self.text_color = (30, 30, 30)
+        self.font = pygame.font.SysFont(None, 48)
+
+        # Prepare the initial score images.
+        self.prep_score()
+        self.prep_high_score()
+        self.prep_level()
+        self.prep_ships()
+
+    def prep_score(self):
+        """Turn the score into a rendered image."""
+        rounded_score = int(round(self.stats.score, -1))
+        score_str = "{:,}".format(rounded_score)
+        self.score_image = self.font.render(score_str, True, self.text_color,
+                                            self.ai_settings.bg_color)
+
+        # Display the score at the top right of the screen.
+        self.score_rect = self.score_image.get_rect()
+        self.score_rect.right = self.screen_rect.right - 20
+        self.score_rect.top = 20
+
+    def prep_high_score(self):
+        """Turn the high score into a rendered image."""
+        high_score = int(round(self.stats.high_score, -1))
+        high_score_str = "{:,}".format(high_score)
+        self.high_score_image = self.font.render(high_score_str, True,
+                                                 self.text_color, self.ai_settings.bg_color)
+
+        # Center the high score at the top of the screen.
+        self.high_score_rect = self.high_score_image.get_rect()
+        self.high_score_rect.centerx = self.screen_rect.centerx
+        self.high_score_rect.top = self.score_rect.top
+
+    def prep_level(self):
+        """Turn the level into a rendered image."""
+        self.level_image = self.font.render(str(self.stats.level), True,
+                                            self.text_color, self.ai_settings.bg_color)
+
+        # Position the level below the score.
+        self.level_rect = self.level_image.get_rect()
+        self.level_rect.right = self.score_rect.right
+        self.level_rect.top = self.score_rect.bottom + 10
+
+    def prep_ships(self):
+        """Show how many ships are left."""
+        self.ships = Group()
+        for ship_number in range(self.stats.ships_left):
+            ship = Ship(self.ai_settings, self.screen)
+            ship.rect.x = 10 + ship_number * ship.rect.width
+            ship.rect.y = 10
+            self.ships.add(ship)
+
+    def show_score(self):
+        """Draw score to the screen."""
+        self.screen.blit(self.score_image, self.score_rect)
+        self.screen.blit(self.high_score_image, self.high_score_rect)
+        self.screen.blit(self.level_image, self.level_rect)
+        # Draw ships.
+        self.ships.draw(self.screen)
\ No newline at end of file
diff --git a/settings.py b/settings.py
new file mode 100644
index 0000000..ea59835
--- /dev/null
+++ b/settings.py
@@ -0,0 +1,48 @@
+class Settings():
+    """A class to store all settings for Alien Invasion."""
+
+    def __init__(self):
+        """Initialize the game's static settings."""
+        # Screen settings.
+        self.screen_width = 1200
+        self.screen_height = 800
+        self.bg_color = (230, 230, 230)
+
+        # Ship settings.
+        self.ship_limit = 3
+
+        # Bullet settings.
+        self.bullet_width = 3
+        self.bullet_height = 15
+        self.bullet_color = 60, 60, 60
+        self.bullets_allowed = 3
+
+        # Alien settings.
+        self.fleet_drop_speed = 10
+
+        # How quickly the game speeds up.
+        self.speedup_scale = 1.1
+        # How quickly the alien point values increase.
+        self.score_scale = 1.5
+
+        self.initialize_dynamic_settings()
+
+    def initialize_dynamic_settings(self):
+        """Initialize settings that change throughout the game."""
+        self.ship_speed_factor = 1.5
+        self.bullet_speed_factor = 3
+        self.alien_speed_factor = 1
+
+        # Scoring.
+        self.alien_points = 50
+
+        # fleet_direction of 1 represents right, -1 represents left.
+        self.fleet_direction = 1
+
+    def increase_speed(self):
+        """Increase speed settings and alien point values."""
+        self.ship_speed_factor *= self.speedup_scale
+        self.bullet_speed_factor *= self.speedup_scale
+        self.alien_speed_factor *= self.speedup_scale
+
+        self.alien_points = int(self.alien_points * self.score_scale)
\ No newline at end of file