Editing Machines (Horizon) (section)

=== Gameplay integration and AI ecosystem ===
Because the machines are established as caretakers of the Earth, the development team programmed each type to exhibit behaviours that match specific roles within a functioning ecosystem.<ref name="HFWReBuilding" /> To dictate machine behaviour, the developers used [[hierarchical task network]] (HTN) planning, allowing the [[Artificial intelligence in video games|artificial intelligence]] (AI) to generate sequences of actions rather than single behaviours. This system enables different machine classes to react dynamically; for instance, Acquisition machines may flee while Combat and Recon machines coordinate to hunt the player.<ref name="BehindTheAIP1" /> To handle navigation, Guerrilla built two distinct systems. Ground-based machines use a [[navigation mesh]] (NavMesh) that adapts to complex terrain changes, while flying machines use a completely separate aerial navigation system based on a runtime-generated [[heightmap]].<ref name="BehindTheAIP2" />

The combat system was designed to facilitate a sense of progression. The ability to shoot off weapons gives the player a temporary "power spike", which is balanced by making these detached weapons heavy and limiting their ammunition.<ref name="GIOrigins" /> The player can also hack or "override" machines using a device attached to [[Aloy]]'s spear.<ref name="AloySpear" /> While some overridden machines can be used as ridable [[Working animal#Riding animals or mounts|mounts]], others will only temporarily fight alongside the player.<ref name="HZDOverrides" /> The developers chose not to let the player directly control the machines' actions after overriding them, ensuring they remain independent entities within the ecosystem.<ref name="ControlMachines" /> In ''Forbidden West'', this mechanic was slightly expanded, allowing the player to specify whether an overridden machine should take aggressive or defensive stances.<ref name="OverrideSubroutines" />

As hardware capabilities improved for ''Forbidden West'', the mechanical ecosystem was significantly expanded. Machines gained increased mobility, allowing them to jump, swim, and cling to surfaces.<ref name="HFWReBuilding" /> The developers also integrated human and machine factions more closely, designing encounters where human enemies actively commandeer machines.<ref name="Evolving" /> To increase the challenge, the game introduced "Apex" variants: heavily armoured, deadlier versions of standard machines.<ref name="GDCHFW" /> Developing the [[virtual reality]] (VR) spin-off ''[[Horizon Call of the Mountain]]'' (2023) required Guerrilla and co-developer [[Firesprite]] to rethink how the player interacts with the mechanical ecosystem. Guerrilla studio director Jan-Bart van Beek noted that giving the player virtual hands created the expectation of realistic, physical interactions; to achieve this, the team used the [[PlayStation VR2]]'s adaptive triggers to simulate the tactile tension of a bowstring and the resistance of climbing handholds.<ref name="UEHCM" /> The developers found that navigating a 3D combat space while fighting massive machines was too cognitively overwhelming for the player in VR. As a solution, they pioneered a lock-on combat system that anchors the player to a circular path around the enemy, allowing for faster and more dynamic dodging without the need for constant manual camera realignment.<ref name="RoadToVR" />

The franchise's mechanical ecosystem is being further adapted for multiplayer-focused spin-offs. For the upcoming ''[[Horizon Steel Frontiers]]'', an [[MMORPG]] developed for [[Mobile game|mobile]] and [[Windows]], developer [[NCSoft]], in collaboration with Guerrilla, restructured the combat to accommodate large-scale cooperative raids heavily inspired by the ''[[Monster Hunter]]'' franchise. To translate the tactical depth of the mainline games into an MMO setting, the developers introduced new mechanics, such as the ability to use a [[grappling hook]] to climb directly onto damaged machine parts to set traps, and the ability to transport detached heavy weapons using mounts.<ref name="HSFMachineCombat" /> Alternatively, Guerrilla's upcoming PS5 and PC [[Cooperative video game|cooperative game]], ''[[Horizon Hunters Gathering]]'', adapts the machines for [[roguelite]] gameplay. Players must coordinate class-based roles to survive "Machine Incursions", wave-based encounters where machines pour out of underground gateways, and navigate "Cauldron Descents", which feature procedurally shifting rooms of machine encounters.<ref name="HHGStyle" />