Originally the game was to be more open world based, with the possibility that each NPC could turn into a Thing at any moment completely randomized. Curtis also hoped the player could get to the end of the game with many, perhaps all, of the NPCs still alive. However, this kind of open-endedness proved impossible to implement, with Curtis, pointing out "It was of course very naïve as it caused huge problems with the squad command menu and dynamically balancing the encounters and resources required for the NPC." Ultimately, NPC characters were scripted to change into Things at specific points, irrespective of the player's actions. This led to a much criticized aspect of the game; the player can test an NPC to find he is human only for him to change into a Thing mere seconds later. Programmer Diarmid Campbell explains;