One of the hallmark features of Project Zomboid is its dedication to realism, and Build 39 takes this to new heights. The update introduces more complex survival mechanics, including a detailed hunger, thirst, and fatigue system. Players must now manage these needs more effectively, making the game significantly more challenging and immersive. For example, the new "moodle" system affects a character's abilities based on their current state of mind, adding a psychological layer to the survival experience. This enhanced realism ensures that players are always on their toes, making every decision count in the fight for survival.