It’s not an action-adventure game without combat in it and Aloy does battle with not just machines, but with other humans as well. In the middle of the top part of the screen is an eye icon, which indicates whether you’re visible or not, as well as how much noise you are making. The eye marker is only shut whenever you are hiding in tall grass; otherwise, it is always open. The markings on either side of the eye are what dictates the noise level, which increases by sprinting and rolling mostly. There are skills which help reduce the noise level of some basic actions.
Whenever you come across an enemy, they tend to not notice you at all, unless you are slinging around explosives, making a lot of noise, or kill a nearby ally of theirs. If an enemy notices you, a gray symbol will appear above them and if they still know you’re there, then that gray circle will gradually fill up as yellow. This will trigger that enemy to investigate, most likely the cause of the disturbance at the source, like if they saw you at a location or if you fired a weapon from a certain spot.
You should be worried if the yellow circle becomes red, as the enemy knows where you are and will come to attack you. However, it is possible to lose the enemy and make them go back to not knowing you’re there, but some enemies have radar that allow them to detect you, even when hiding in tall grass (Scrappers and Thunderjaws are two such machines). It is possible to destroy these radars, makin it a bit easier to keep stealthy.
There are two main ways to defeat enemies in this game, either with head-on combat or via stealth. The latter tends to go away as you progress further into the game, as machines will get bigger and stronger, making it to where stealth would take way too long to down the enemy. In order to stealth kill an enemy, you need to have purchased the Silent Strike skill, which costs one point. Sneak up to an enemy to receive a L1 button prompt to perform the maneuver. Note that this won’t kill stronger machines and it only works on small-to-medium sized ones; large ones like the Thunderjaw and Stormbird can’t be Silent Striked. Also, elite/heavy human enemies (they have a skull icon when you tag them) require the Leader Strike skill in order to perform a Silent Strike on them.
Battling Enemies Head-On
The other method of fighting enemies is by attacking them head-on, where you need to use your weapons and other tools. For human enemies, the fight is simple, as you can aim for their head to do the most damage, with most humans being killed from a simple headshot. Human enemies usually come in two varieties, those who run up and melee you and those that strike with bows from far away. There are some deviations, like heavy/elites with powerful weaponry, but those fall into the ranged category.
Machines, on the other hand, have a lot of variations among them, since there are so many of them. While they have their weak points, which you can highlight temporarily by scanning them with your Focus, some of them are much harder to hit due to their placements or by having armor protecting them. Take a look at the Snapmaw, as an example, which have a sac on the underside of their neck that can be harder to hit, as well as Blaze Canisters on its back that sometimes have armor.
Fighting a new machine for the first time will always be troubling, as you don’t know what they are capable of or how they act. Thus, you should use your first few encounters to study them and learn how they tick, so you get to a point where you can fight them without having to constantly chug potions or use your medicine bag. Hitting enemies in a weakpoint will display the damage with a green arrow, while striking a strong point will display the damage with a red arrow.
Upon successfully killing an enemy, you will gain experience points directly proportional to the enemy you fought. That means something like a normal human or smaller machine will yield less experience than an elite/heavy or a Thunderjaw. There are a few extra bits for experience, like killing an enemy while it’s burning or frozen, as well as doing it in stealth, but the bulk of the experience comes from the actual kill. Once you have accrued enough experience, you will level up, upon which you will gain a Skill Point and an extra ten max HP.
During combat, holding down the L1 button will access the weapon wheel, which is an integral part of fighting. You can only place four weapons on the wheel, meaning you might have to leave out one or two extras. Note that the bows have three different ammo types, but they only count as one weapon. You switched weapons by pressing left/up/right/down with the left analog stick and in the case of multiple ammo types, just slide the stick in that one direction ever so slightly to highlight the ammo type you want. One thing that happens whenever the weapon wheel is up is that the action in-game slows down, and you actually retain some abilities like rolling and item use.