import pygame
pygame.init()
screen = pygame.display.set_mode((900, 500))
clock = pygame.time.Clock()

player = pygame.Rect(40, 100, 40, 40)
cactus = pygame.Rect(800, 460, 30, 40)
gravity = 0

while True:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            exit()
    
    keys = pygame.key.get_pressed()
    if keys[pygame.K_SPACE] and player.bottom >= 400:
        gravity = -20
    
    gravity += 1
    player.y += gravity
    if player.bottom > 500:
        player.bottom = 500
    
    cactus.x -= 10
    if cactus.x < -50:
        cactus.x = 900
    
    screen.fill((255,255,255))
    pygame.draw.rect(screen, (0,255,0), player)
    pygame.draw.rect(screen, (255,0,0), cactus)
    pygame.display.flip()
    clock.tick(60)