import pygame
import traceback
import random


class Player:
    def __init__(self, x, y):
        self.x = x
        self.y = y

    def tick(self, pressed, _entities):
        if pressed[pygame.K_LEFT]:
            self.x -= 2
        if pressed[pygame.K_RIGHT]:
            self.x += 2
        if pressed[pygame.K_UP]:
            self.y -= 2
        if pressed[pygame.K_DOWN]:
            self.y += 2

    def draw(self, screen):
        pygame.draw.rect(screen,
                         (0, 128, 255),  # color (r,g,b)
                         (self.x, self.y, 16, 16))  # rect (x,y,w,h)


class Enemy:
    def __init__(self, x, y):
        self.x = x
        self.y = y

    def tick(self, _pressed, entities):
        player = entities[0]
        dx = player.x - self.x
        dy = player.y - self.y
        if dx < 0:
            self.x -= 1
        elif dx > 0:
            self.x += 1
        if dy < 0:
            self.y -= 1
        elif dy > 0:
            self.y += 1

    def draw(self, screen):
        pygame.draw.rect(screen,
                         (255, 0, 0),  # color (r,g,b)
                         (self.x, self.y, 8, 8))  # rect (x,y,w,h)


class RandomEnemy:
    def __init__(self, x, y):
        self.x = x
        self.y = y

    def tick(self, _pressed, _entities):
        self.x += random.randint(-2, 2)
        self.y += random.randint(-2, 2)

    def draw(self, screen):
        pygame.draw.rect(screen,
                         (255, 0, 0),  # color (r,g,b)
                         (self.x, self.y, 16, 16))  # rect (x,y,w,h)


def game_step(screen, pressed, entities):
    # Simulation
    for ent in entities:
        ent.tick(pressed, entities)

    # Rendering
    for ent in entities:
        ent.draw(screen)


def play():
    pygame.init()
    screen = pygame.display.set_mode((320, 240))  # "Surface"
    done = False
    clock = pygame.time.Clock()
    entities = [Player(50, 50),
                Enemy(100, 100),
                RandomEnemy(75, 150)]
    while not done:
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                done = True
        pressed = pygame.key.get_pressed()
        if pressed[pygame.K_ESCAPE]:
            done = True
        screen.fill((0, 0, 0))
        game_step(screen, pressed, entities)
        pygame.display.flip()
        clock.tick(60)
    pygame.quit()


try:
    play()
except Exception:
    traceback.print_exc()
    pygame.quit()