Walkers, and although each one requires a specific strategy to defeat, the principle is the same; weaken it with gunfire before burning it. One of the main features of The Things gameplay is the inclusion of multiple NPCs who join Blake at various points throughout the game. At any one time, the player can control up to four characters; Blake and three NPCs. There are three types of NPC in the game; engineers, soldiers and medics. Engineers can repair fuse boxes, which control locked doors, computers and save points. Soldiers have more health, and are better shots than engineers or medics. They are thus more suited to combat. Medics are capable of healing both Blake and any other injured NPCs, and carry unlimited health packs. The player can issue basic commands to each NPC, such as ordering them to follow Blake, ordering them to remain where they are, ordering them to give Blake their weapon, and, in the case of engineers, ordering them to fix a fuse box. NPC AI is determined primarily by the "Fear/trust system". The trust system determines whether the NPCs will follow Blake's orders and join him in combat. To do so, the player must ensure the NPC trusts Blake, and does not suspect him of being a Thing. NPCs have four levels of trust; red, amber, green and 100%. Red means they are convinced Blake is a Thing and will attack him. Amber means they are not sure if he is a Thing, and although they won't attack him, they won't follow his orders. Green means they trust him and will follow his orders. 100% means they have complete faith in him, will follow his orders, and even if he attacks another NPC, they will support him. To gain the trust of NPCs, Blake can give them weapons and ammo, heal them, put himself at risk to protect them, or use a blood test kit on himself to prove he is not a Thing. Actions which deplete trust include accidentally shooting teammates, taking away teammate's weapons or ammo, or pointing a weapon at them for a sustained period of time to force them to do something. The fear system dictates how scared a given NPC is. There are three levels of fear; normal, scared and "Crack-up". When an NPC enters "Crack-up" mode, Blake has only a limited amount of time to reduce their fear level,