Pygame Dual Stick Shooter

I want to create a dual stick shooter, (Games like "Dead Ops Arcade" in the new Black Ops, and Smash Tv).

The controls will be movement with WASD, aiming with the mouse, and shooting by clicking the mouse.
But I want to have an enemy that will follow my character, what would be the best way to do this?

And here's my code:


import pygame, sys
from pygame.locals import *

bif = "bg.jpg"

pygame.init()
pygame.display.set_caption('Game Title')
screen=pygame.display.set_mode((640,360),0,32)

background=pygame.image.load(bif).convert()

x,y=0,0
movex, movey=0,0

points=[(50,50),(100,100),(75,100)]
colour=(0,255,0)

while True:
    screen.blit(background, (0,0))
    screen.lock()
    #Lock screen so nothing inteferes with draw.
    sqaure = pygame.draw.rect(screen, (100,100,100), Rect((x,y),(5,5)))
    pygame.draw.polygon(screen, colour, points)
    #enemy = pygame.draw.rect(screen, (255,0,0), Rect((50,50),(45,45)))
    screen.unlock()

    for event in pygame.event.get():
        if event.type == QUIT:
            pygame.quit()
            sys.exit()
        if event.type == KEYDOWN:
            if event.key == K_a:
                movex=-1
            elif event.key == K_d:
                movex=+1
            elif event.key == K_w:
                movey=-1
            elif event.key == K_s:
                movey=+1
        if event.type==KEYUP:
            if event.key == K_a:
                movex=-0
            elif event.key == K_d:
                movex=+0
            elif event.key == K_w:
                movey=-0
            elif event.key == K_s:
                movey=+0
    x+=movex
    y+=movey

   
    #screen.blit(sqaure, (x,y))

    pygame.display.update()

>>7
"
U+0022 QUOTATION MARK

Looks valid to me.