Some zombie game, idk

This is my second game, a top down shooter about killing zombies. I made it while I was bored and had no internet... Anyway, you're guy or girl. However you like to call yourself and you must kill zombies to survive. Pretty basic, huh? Also, the zombie speed up while your score gets bigger. 

You control the character using the arrow keys, you can shoot pressing space and if you hold alt, your speed will increase 3 times. You can run away from the zombies and fool them to kill themselves, but everytime you do that, your score will decrease by one. (you can even have negative score, lol)