All enemies are invisible. The only way to know where to fire your weapon is to look on the enemy's screen. Pretty interesting concept! You can sign up for free beta access on the website I believe. This is one you will need to play locally, and a reason why having a brother or sister comes in handy!
We used to call this screenlooking instead of screencheating when we played local games all day when I was younger. Our favorite was two Xbox systems hooked up together, one in the basement and one on the main level. We had four people on one team and four on another on separate systems and floors altogether to prevent screenlooking.