так лучше

import pygame
from random import randint
pygame.init()

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

def sign (d):
    if d>0 : return 1
    else: return -1
global score
global flag
flag=False
score= 0
size = [800,600]
screen = pygame.display.set_mode(size)
done = False
class NoTarget:
    def __init__ (self):
        self.x = randint(15,800-15)
        self.y = randint(15,600-15)
        self.r = randint(2,15)
        self.color = (255,0,0)
    def move (self):
        pygame.draw.rect(screen,self.color,([self.x,self.y],(15,15)),0)
    def intersection(self):
        if Gamer[1]+15>self.y and Gamer[1]<self.y+15 and Gamer[0]+15>self.x and Gamer[0]<self.x+15:
            return True
        return False
    def ChangeOfStation(self):
            self.x = randint(15,800-15)
            self.y = randint(15,600-15)
class Target:
    def __init__ (self):
        self.x = randint(15,800-15)
        self.y = randint(15,600-15)
        self.r = randint(2,15)
        self.color = (0,100,255)
    def move (self):
        pygame.draw.rect(screen,self.color,([self.x,self.y],(15,15)),0)
    def intersection(self):
        if Gamer[1]+15>self.y and Gamer[1]<self.y+15 and Gamer[0]+15>self.x and Gamer[0]<self.x+15:
            return True
        return False
    def ChangeOfStation(self):
        self.x = randint(15,800-15)
        self.y = randint(15,600-15)
myfont = pygame.font.SysFont("monospace", 50)
clock = pygame.time.Clock()

c = []
for i in range(score+1):
    c.append(NoTarget())
target = Target()


while done == False:
    # обработчик событий
    clock.tick(90)
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            done = True
        elif event.type == pygame.MOUSEMOTION:
            Gamer = pygame.mouse.get_pos()
        elif event.type ==pygame.KEYDOWN:
            key = pygame.key.get_pressed()
            if key[pygame.K_ESCAPE] == 1:
                done = True




    # логика







    # перерисовка
    screen.fill([0,0,0])

    label = myfont.render(str(int(score)), 1, RED)
    screen.blit(label, (0, 0))
    if target.intersection() and not flag:
        score+=1
        c.append(NoTarget())
        target.ChangeOfStation()
        for i in range(score+1):
            c[i].ChangeOfStation()
    for i in range(score+1):
            c[i].move()
            if c[i].intersection():
                            flag=True

    if flag:
        label = myfont.render("GAME OVER", 1, RED)
        screen.blit(label, (100, 100))
        labelOne = myfont.render("PRESS 'ESCAPE' TO EXIT", 1, RED)
        screen.blit(labelOne, (100, 200))
    target.move()
    pygame.draw.rect(screen,(255,255,255),(Gamer,(15,15)),0)
    pygame.display.flip()
pygame.quit()