Creating a complete endless runner game involves multiple components and can be quite extensive. Here's a simplified example using the Pygame library. Before running this code, make sure you have Pygame installed (`pip install pygame`).

```python
import pygame
import random
import sys

# Initialize Pygame
pygame.init()

# Constants
WIDTH, HEIGHT = 800, 600
FPS = 60
PLAYER_SIZE = 50
OBSTACLE_SIZE = 50
POWERUP_SIZE = 30
PLAYER_SPEED = 5
OBSTACLE_SPEED = 5
POWERUP_SPEED = 5

# Colors
WHITE = (255, 255, 255)
RED = (255, 0, 0)
BLUE = (0, 0, 255)

# Create the game window
screen = pygame.display.set_mode((WIDTH, HEIGHT))
pygame.display.set_caption("Endless Runner Game")

# Load images
player_image = pygame.Surface((PLAYER_SIZE, PLAYER_SIZE))
player_image.fill(RED)

obstacle_image = pygame.Surface((OBSTACLE_SIZE, OBSTACLE_SIZE))
obstacle_image.fill(WHITE)

powerup_image = pygame.Surface((POWERUP_SIZE, POWERUP_SIZE))
powerup_image.fill(BLUE)

# Game variables
player = pygame.Rect(WIDTH // 2 - PLAYER_SIZE // 2, HEIGHT - PLAYER_SIZE - 10, PLAYER_SIZE, PLAYER_SIZE)
obstacles = []
powerups = []
score = 0

# Clock to control the frame rate
clock = pygame.time.Clock()

# Game loop
while True:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            sys.exit()

    # Move player
    keys = pygame.key.get_pressed()
    if keys[pygame.K_LEFT] and player.left > 0:
        player.x -= PLAYER_SPEED
    if keys[pygame.K_RIGHT] and player.right < WIDTH:
        player.x += PLAYER_SPEED

    # Generate obstacles and power-ups
    if random.randint(1, 100) <= 5:
        obstacle = pygame.Rect(random.randint(0, WIDTH - OBSTACLE_SIZE), 0, OBSTACLE_SIZE, OBSTACLE_SIZE)
        obstacles.append(obstacle)

    if random.randint(1, 100) <= 2:
        powerup = pygame.Rect(random.randint(0, WIDTH - POWERUP_SIZE), 0, POWERUP_SIZE, POWERUP_SIZE)
        powerups.append(powerup)

    # Move obstacles and power-ups
    for obstacle in obstacles:
        obstacle.y += OBSTACLE_SPEED

    for powerup in powerups:
        powerup.y += POWERUP_SPEED

    # Check for collisions
    for obstacle in obstacles:
        if player.colliderect(obstacle):
            pygame.quit()
            sys.exit()

    for powerup in powerups:
        if player.colliderect(powerup):
            powerups.remove(powerup)
            score += 10

    # Remove obstacles and power-ups that are out of the screen
    obstacles = [obstacle for obstacle in obstacles if obstacle.y < HEIGHT]
    powerups = [powerup for powerup in powerups if powerup.y < HEIGHT]

    # Draw everything
    screen.fill((0, 0, 0))
    pygame.draw.rect(screen, RED, player)
    for obstacle in obstacles:
        pygame.draw.rect(screen, WHITE, obstacle)
    for powerup in powerups:
        pygame.draw.rect(screen, BLUE, powerup)

    # Display the score
    font = pygame.font.Font(None, 36)
    score_text = font.render(f"Score: {score}", True, WHITE)
    screen.blit(score_text, (10, 10))

    # Update the display
    pygame.display.flip()

    # Control the frame rate
    clock.tick(FPS)
```

This is a simple endless runner game where the player can move left and right to avoid obstacles. Power-ups increase the score when collected. The game will end if the player collides with an obstacle. Note that this is a basic example, and you can expand and improve upon it by adding more features, graphics, and refining the gameplay.