Hit and Score

Part of the Sprites and Images section of Coddy's Pygame journey. Lesson 33 of 36.

Lasers against enemies is a group against a group, with groupcollide. A laser's picture is a thin bolt in the middle of a 48 pixel square, so a Rect test would let a laser 20 pixels to the side destroy an enemy. Test the pictures with masks:

hits = pygame.sprite.groupcollide(enemies, lasers, True, True, pygame.sprite.collide_mask)
for enemy in hits:
    score += 10

The fifth argument is the test, as with spritecollide. Give Laser and Enemy each a self.mask = pygame.mask.from_surface(self.image), so the masks are made once, not on every test.

Looping over hits goes through the destroyed enemies, one by one: each is worth 10 points. Show the score at the top left with font = pygame.font.Font(None, 32), made once before the loop.

Challenge

Medium

Give Laser and Enemy a self.mask.
Make score = 0 and a font of size 32 before the loop.
After the updates, collide enemies with lasers using pygame.sprite.collide_mask, killing both, and add 10 to score for every enemy hit.
Draw Score: and the score at (10, 10), in (240, 240, 240).

Try it yourself

import random
import pygame

pygame.init()
screen = pygame.display.set_mode((640, 480))
pygame.display.set_caption("Star Patrol")
clock = pygame.time.Clock()

ship_image = pygame.image.load("assets/images/ship.png").convert_alpha()
laser_image = pygame.image.load("assets/images/laser.png").convert_alpha()
red_image = pygame.image.load("assets/images/enemy_red.png").convert_alpha()


class Player(pygame.sprite.Sprite):
    def __init__(self):
        super().__init__()
        self.image = ship_image
        self.rect = self.image.get_rect(midbottom=(320, 470))

    def update(self):
        keys = pygame.key.get_pressed()
        if keys[pygame.K_LEFT]:
            self.rect.x -= 6
        if keys[pygame.K_RIGHT]:
            self.rect.x += 6
        self.rect.clamp_ip(screen.get_rect())


class Laser(pygame.sprite.Sprite):
    def __init__(self, x, y):
        super().__init__()
        self.image = laser_image
        self.rect = self.image.get_rect(midbottom=(x, y))

    def update(self):
        self.rect.y -= 10
        if self.rect.bottom < 0:
            self.kill()


class Enemy(pygame.sprite.Sprite):
    def __init__(self, image, x, y, speed):
        super().__init__()
        self.image = image
        self.rect = self.image.get_rect(center=(x, y))
        self.speed = speed

    def update(self):
        self.rect.y += self.speed


def spawn_wave(image, count, speed):
    for i in range(count):
        x = random.randint(40, 600)
        enemies.add(Enemy(image, x, -40 - i * 120, speed))


player = Player()
lasers = pygame.sprite.Group()
enemies = pygame.sprite.Group()
last_shot = 0
spawn_wave(red_image, 6, 2)

running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False

    player.update()
    keys = pygame.key.get_pressed()
    now = pygame.time.get_ticks()
    if keys[pygame.K_SPACE] and now - last_shot >= 250:
        lasers.add(Laser(player.rect.centerx, player.rect.top))
        last_shot = now
    lasers.update()
    enemies.update()
    for enemy in enemies:
        if enemy.rect.top > 480:
            enemy.kill()

    screen.fill((12, 14, 30))
    enemies.draw(screen)
    lasers.draw(screen)
    screen.blit(player.image, player.rect)
    pygame.display.flip()
    clock.tick(60)

pygame.quit()