import pygame
import random

# 初始化
pygame.init()
W, H = 800, 600
screen = pygame.display.set_mode((W, H))
pygame.display.set_caption("二维射击")
clock = pygame.time.Clock()

# 颜色
BLACK = (0, 0, 0)
WHITE = (255, 255, 255)
RED = (255, 0, 0)
BLUE = (0, 100, 255)

# 玩家
player_x, player_y = W//2, H//2
player_speed = 5
player_r = 20

# 子弹列表
bullets = []
bullet_speed = 10

# 敌人列表
enemies = []
enemy_speed = 2

running = True

while running:
    clock.tick(60)
    screen.fill(BLACK)

    # 事件监听
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
        # 鼠标点击发射子弹
        if event.type == pygame.MOUSEBUTTONDOWN:
            mx, my = pygame.mouse.get_pos()
            dx = mx - player_x
            dy = my - player_y
            dis = (dx**2 + dy**2)**0.5
            if dis != 0:
                bullets.append([player_x, player_y, dx/dis*bullet_speed, dy/dis*bullet_speed])

    # WASD移动
    keys = pygame.key.get_pressed()
    if keys[pygame.K_w] and player_y > player_r:
        player_y -= player_speed
    if keys[pygame.K_s] and player_y < H-player_r:
        player_y += player_speed
    if keys[pygame.K_a] and player_x > player_r:
        player_x -= player_speed
    if keys[pygame.K_d] and player_x < W-player_r:
        player_x += player_speed

    # 随机生成敌人
    if random.randint(1,40) == 1:
        side = random.choice([0,1,2,3])
        if side == 0:
            ex, ey = random.randint(0,W), -20
        elif side == 1:
            ex, ey = random.randint(0,W), H+20
        elif side == 2:
            ex, ey = -20, random.randint(0,H)
        else:
            ex, ey = W+20, random.randint(0,H)
        enemies.append([ex, ey])

    # 更新子弹
    new_bullets = []
    for b in bullets:
        b[0] += b[2]
        b[1] += b[3]
        if 0 < b[0] < W and 0 < b[1] < H:
            new_bullets.append(b)
    bullets = new_bullets

    # 更新敌人+碰撞检测
    new_enemies = []
    for e in enemies:
        edx = player_x - e[0]
        edy = player_y - e[1]
        edis = (edx**2 + edy**2)**0.5
        if edis != 0:
            e[0] += edx/edis * enemy_speed
            e[1] += edy/edis * enemy_speed

        # 子弹打中敌人
        hit = False
        for b in bullets[:]:
            if (e[0]-b[0])**2 + (e[1]-b[1])**2 < 400:
                bullets.remove(b)
                hit = True
                break
        if not hit:
            new_enemies.append(e)
    enemies = new_enemies

    # 绘制
    pygame.draw.circle(screen, BLUE, (player_x, player_y), player_r)
    for b in bullets:
        pygame.draw.circle(screen, WHITE, (int(b[0]), int(b[1])), 5)
    for e in enemies:
        pygame.draw.circle(screen, RED, (int(e[0]), int(e[1])), 18)

    pygame.display.flip()

pygame.quit()