A difficulty setting changes several distinct systems at once, and the choice of which ones to adjust is a design statement. Two games offering the same options can mean entirely different things by them.
Numeric scaling is the cheapest lever
Multiplying enemy health and damage requires no new content and can be applied uniformly across a whole game in a single pass.
It reliably changes how long encounters last and how unforgiving mistakes are, which is why almost every difficulty system includes it somewhere.
Taken alone it produces a poor result, since inflated health turns a tense fight into a slow one without demanding anything new from the player.
Behavioural changes alter what is being tested
Higher settings can make enemies attack in coordinated groups, react faster to being spotted or use abilities they otherwise hold back.
These changes ask for different play rather than more of the same, and they are what distinguishes a considered difficulty system from a scaled one.
They are also expensive, because each behaviour must be authored and tested separately, so they appear mainly in games where combat is the central pillar.
Resource availability sets the margin for error
Adjusting how much ammunition, healing or currency a player finds changes the whole rhythm of a game without touching any individual encounter.
Scarcity forces planning between fights and makes retreat a real option, which shifts the challenge from execution toward management.
Survival games rely almost entirely on this lever, and it explains why their harder modes feel different in kind rather than simply tighter.
Hidden assists run underneath the label
Many games quietly help the player, granting a brief window of invulnerability after a hit or ensuring the final portion of health absorbs more damage.
Aim assistance, forgiving hit detection and adjusted enemy accuracy operate on the same principle, smoothing an experience without announcing it.
These are usually strongest on lower settings and reduced or removed on higher ones, which is part of why the jump between them can feel abrupt.
Dynamic adjustment is contentious
Some systems respond to performance directly, easing off after repeated failure or applying pressure when a player is progressing comfortably.
Done subtly this keeps more players engaged, but players who notice it often feel their achievement has been undermined by the game meeting them halfway.
The current preference is toward explicit granular options, letting a player adjust individual systems themselves rather than trusting a hidden hand to do it.