Instead of playing as Master Chief you play as an elite. You have other elites on your side, fight spartans and marines. Note: this is for Halo PC (Combat Evolved) not Halo CE( Custom Edition )
Same as 3.5 but now you can crouch in all difficulties. In easy and normal you have to pick up the plasma rifle from the dead elites body (not the elite that gets blown up by an exploding door). Unfortunatly fixing this bug created a new bug. You may end up with three weapons for some reason. This is more likely to happen in higher difficulties. Have fun!