Do you want 500 extra achievements on your steam account and as easy as possible? Look no further!!
Buy this game. Only $0.79.
Play the game and load it up on easy.
Run the the end of the street you are put on and once there, turn around. When you're looking back if you step to your left there is a sidewlk. standing on it makes all "Phantoms" walk on that path and won't attack from any other angle. Keep shooting until all achievements are unlocked.
You can't pause or leave the game!!!
Technically the last achievement isn't to have killed 500 of them but to have killed 500 without pausing or leaving the game. if you pause you get sent back to 0 and have to climb to where you were before you start recieving achievements again.