H a n d s o n, p r o j e c t b a s e d

Displaying the Level
To display the player’s level in the game, we first need an attribute in 
GameStats
representing the current level. To reset the level at the start of 
each new game, initialize it in 
reset_stats()
:
def reset_stats(self):
"""Initialize statistics that can change during the game."""
self.ships_left = self.settings.ship_limit
alien_invasion.py
game_stats.py

---

Scoring
297
self.score = 0
self.level = 1
To have 
Scoreboard
display the current level, we call a new method, 
prep 
_level()
, from 
__init__()
:
def __init__(self, ai_game):
--snip--
self.prep_high_score()
self.prep_level()
Here’s 
prep_level()
:
def prep_level(self):
"""Turn the level into a rendered image."""
level_str = str(self.stats.level)
u
self.level_image = self.font.render(level_str, True,
self.text_color, self.settings.bg_color)
# Position the level below the score.
self.level_rect = self.level_image.get_rect()
v
self.level_rect.right = self.score_rect.right
w
self.level_rect.top = self.score_rect.bottom + 10
The 
prep_level()
method creates an image from the value stored in 
stats.level
u and sets the image’s 
right
attribute to match the score’s 
right
attribute v. It then sets the 
top
attribute 10 pixels beneath the bottom of 
the score image to leave space between the score and the level w.
We also need to update 
show_score()
:
def show_score(self):
"""Draw scores and level 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)
This new line draws the level image to the screen.
We’ll increment 
stats.level
and update the level image in 
_check_bullet 
_alien_collisions()
:
def _check_bullet_alien_collisions(self):
--snip--
if not self.aliens:
# Destroy existing bullets and create new fleet.
self.bullets.empty()
self._create_fleet()
self.settings.increase_speed()
# Increase level.
self.stats.level += 1
self.sb.prep_level()
scoreboard.py
scoreboard.py
scoreboard.py
alien_invasion.py

---

298
Chapter 14
If a fleet is destroyed, we increment the value of 
stats.level
and call 
prep_level()
to make sure the new level displays correctly.
To ensure the level image updates properly at the start of a new game, 
we also call 
prep_level()
when the player clicks the Play button:
def _check_play_button(self, mouse_pos):
--snip--
if button_clicked and not self.stats.game_active:
--snip--
self.sb.prep_score()
self.sb.prep_level()
--snip--
We call 
prep_level()
right after calling 
prep_score()
.
Now you’ll see how many levels you’ve completed, as shown in 
Figure 14-5.
Figure 14-5: The current level appears just below the current score.
n o T e
 
In some classic games, the scores have labels, such as Score, High Score, and Level. 
We’ve omitted these labels because the meaning of each number becomes clear once 
you’ve played the game. To include these labels, add them to the score strings just 
before the calls to 
font.render()
 in 
Scoreboard
.