Tuesday, February 1, 2011

Game difficulty (Part 2)

The simplest means to implement varying difficult in a game is to use a "difficulty level". Take the example of Doom. Upon starting the game, you pick how hard you want the game to be, and based on this difficulty several factors are be changed. At higher difficulties, there were more enemies, and often more difficult enemies placed in levels. Some health pickups would be missing at higher levels, and potentially even weapons. At lower difficulties it was even possible for some areas of a level to be avoided, by giving players access to the end of the level through a keycard in a more easily accessible location.

In more generic terms, the amount of support that the player receives (whether health, weaponry, allies, ammunition or whatever else might help them prevail) might be higher on easier difficulty levels, and reduced on higher ones. The amount of damage that a player takes might vary according with difficulty, as might the amount of damage that can be taken by enemies.  The intelligence of enemies might change, and their numbers could increase with higher difficulties.

If you're really tough, you'll fight three of them

In Doom the difficulty was chosen at the start of the game (technically at the start of each episode) and that determined the difficulty for the entire episode. If the player reached a point where the game was too difficult for them, they potentially had no recourse except to start from the beginning. Hardly desirable if they've played the game for numerous hours. Thus many modern games allow the player to change the difficulty part way through the game. This means that typically difficulty modifies the behaviour or strength of enemies rather than their number. It is also hard in this case to reduce resources given to the player, as you can't very well just make resources vanish into thin air if the player changes the difficulty up, or make them magically appear if the difficulty goes down. That said, it might be possible to adjust the effect of each acquired resource - each ammo clip might give half (or twice) as much ammunition to the player dependent on the difficulty level.

It is potentially possible to adjust the number of enemies dynamically if enemies are created ahead of the player out of sight. In this situation, the number and type of enemy are created according to the current difficulty level, before the player prior to the player reaching a location with visibility of that area.  In the simplest situation, that might mean upon started a new level, but in some cases, enemies can be "spawned" as the player reaches a choke point before the next encounter. This may not be possible depending upon the type of game (and its level design), but this could result in the difficulty adjusting as soon as the player reaches the next "encounter" area. For example, a player traveling through a valley reaches a pass that leads to the site of the the enemy camp. While in the pass, the player has no visibility of the camp, and at this moment the enemies are spawned at the camp depending on the current difficulty level. As an added step, it might also be possible to have an autosave point before the enemies are generated, thus giving the player the option to decrease the challenge of the encounter should they need.

The "world map" - one possible place to spawn enemies

These are typically the most basic means to implement difficulty in games: make the enemies tougher, and make more of them. The problem is that this doesn't necessarily make for the game actually being more interesting, and in some cases serves to destroy the reality created by the game. Case in point here are the "Juggernauts" in Modern Warfare 2's Spec Ops missions. Enemies that can take multiple headshots from a sniper rifle simply have no place in the reality of a modern "realistic" FPS game. Increasing the health of enemies in action RPGs (Diablo and its clones) frequently does little to increase the difficulty of the game, also see the original Mass Effect for a demonstration of this point. Giving enemies more health simply made them take longer to kill rather than actually increasing the challenge for the player.

Increasing the "difficulty" just made him take more bullets

So having discussed basic elements of modifying a game's difficulty, in the next post I'll discuss alternatives and issues relating to these difficulty levels.


  1. RE: This part;

    "Case in point here are the "Juggernauts" in Modern Warfare 2's Spec Ops missions. Enemies that can take multiple headshots from a sniper rifle simply have no place in the reality of a modern "realistic" FPS game."

    I throw back to an old argument I always had thrown at me when dealing with more realistic elements of some games, that being arguing realism in a virtual world is a moot point. Already in MW2, you have the "If I stay behind cover long enough, despite how many bullets I just took, I'll be at perfect health again", or as another example, when my target doesn't die because I shot them in the ankle with a .50 cal sniper rifle. You'd instead be picking up what was left of your foot and lower leg and crawling to cover.

    Resolving this point lies in what the makers of MW2 intended,, true realism or action-movie realism,, and I think the latter. Where the Juggernauts enter is to create a new, unique challenge within that game environment, one in which I don't think the designers are attempting to create "true" realism. This challenge itself presents an enemy which, unlike all standard enemies which take cover often and hide from your fire, charges through the crossfire unrelentingly, forcing a very quick rethink of tactics, something highly challenging in a game I believe to be aimed at what you describe as people "who really don't have the patience to perfect their skills, or the dedication to learn and study complex tactics".

    And indeed, as I believe you pointed out to me, the pursuit of realism in the case of cover based systems does not always create a better game.

  2. Fair call, and you make interesting points, but I still stand by my assessment. The problem is that the Juggernauts are so far removed from the fiction presented in the game that it doesn't make sense. People magically heal when in cover, okay, it's totally implausible from any sort of realism, but it's there for mechanic reasons.

    The main issue I have is that the juggernauts are ridiculous because they're inconsistent with the reality as presented by the game. Furthermore, they don't really force the player to change tactics significantly, just rapidly unload more ammunition into their head until they die, and before they can close the gap to the player and kill them. If the designers are going to introduce something that completely breaks the "reality" of the game, then they damn well better do something more interesting with the gameplay as a result than "do what you've been doing... just more".