flappy birb simplified without images

import pygame
from random import randint

BLACK = (0, 0, 0)
WHITE = (255, 255, 255)
GREEN = (0, 255, 0)
RED = (255, 0, 0)

pygame.init()

size = 700, 500
screen = pygame.display.set_mode(size)
pygame.display.set_caption("Flappy bird")

done = False
clock = pygame.time.Clock()

def ball(x, y):
    #radius of 20px
    pygame.draw.circle(screen, BLACK, [x, y], 20)

def gameover():
    font = pygame.font.SysFont(None, 55)
    text = font.render("Game Over", True, RED)
    screen.blit(text, [150, 250])

def obstacles(xloc, yloc, xsize, ysize):
    pygame.draw.rect(screen, GREEN, [xloc, yloc, xsize, ysize])
    pygame.draw.rect(screen, GREEN, [xloc, int(yloc+ysize+space), xsize, ysize+500])

#when ball between 2 points on screen, increase score
def Score(score):
    font = pygame.font.SysFont(None, 55)
    text = font.render("Score:" + str(score), True, BLACK)
    screen.blit(text, [0,0])


x = 350
y = 250
x_speed = 0
y_speed = 0
ground = 477
xloc = 700
yloc = 0
xsize = 70
ysize = randint(0, 350)
#size of space between 2 blocks
space = 150
obspeed = 2
score= 0

while not done:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            done = True

        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_UP:
                y_speed = -10

        if event.type == pygame.KEYUP:
            if event.key == pygame.K_UP:
                y_speed = 5

    screen.fill(WHITE)
    obstacles(xloc, yloc, xsize, ysize)
    ball(x, y)
    Score(score)

    y += y_speed
    xloc -= obspeed

    if y > ground:
        gameover()
        y_speed = 0
        obspeed = 0

    if x+20 > xloc and y-20 < ysize and x-15 < xsize+xloc:
        gameover()
        y_speed = 0
        obspeed = 0

    if x+20 > xloc and y+20 < ysize and x-15 < xsize+xloc:
        gameover()
        y_speed = 0
        obspeed = 0

    if xloc < -80:
        xloc = 700
        ysize = randint(0, 350)

    if x > xloc and  x < xloc+3:
        score = score + 1

    pygame.display.flip()
    clock.tick(60)
pygame.quit()