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  • Replayability: Game Mechanics As Periodic Dilemma Generators

    - Narek Aghekyan

  • Examples of PDGs

    We should note that it is better to build the periodic dilemma generator into the core mechanics. Yes, PDG can be built in the level design, or in the meta-game, but first and foremost it should be built into the core part of the game mechanics - in the core loop of the game. In order to understand what it means to build a PDG inside of the core mechanics, let's analyze a couple of examples to demonstrate how PDGs act as a system built into the core loop of games or even in game genres.

    Fighter Games

    In his book Steve Swink analyses fighter game combat mechanics on the example of Street Fighter II [2]. He explains that when you press "one of six attack buttons" on a joystick the game starts to "play back an animation which changes the shape of the avatar". During playing the animation "the player is locked out of further input until the animation is complete". "For the "light" attacks, the duration is very short and will not interrupt the correction cycle of the walking mechanic. The heavy attacks can take almost one second to complete, however, disrupting the continuity of control."

    So where is the PDG?

    1. Meaningful choices. In the menus of fighting games for every attack it is known how much the damage is, and how many frames the animation will play, i.e. how many frames the input will be locked. Hence, the player attacks are both informed and have consequences.
    2. Dilemmatic choices. The choice to attack is always dilemmatic. Player knows that during the attack either he will damage the opponent, or he will get locked by exposing himself to the opponent's attacks. Another dilemma is following: he can choose to attack stronger, but get locked longer. This clearly creates a risk-reward situation for the player. Jesse Schell calls it triangularity -  when a player is faced with a choice between two actions: one that is low risk and gives a low reward, and another that is risky but has a bigger payoff. [7]
    3. Unpredictable outcome. Till the last moment of the fight neither of the players knows who will win the round even if players health points (HP) are significantly different (one is low HP and other one is almost full HP). A comeback is usually a possible option if player skills are evenly matched.

    There are many fighting games such as Street Fighter, Mortal Kombat, Tekken, Killer Instinct, etc. All these games are inherently interesting, because they have the above mentioned PDG implemented in the core of the combat mechanics. But also these games are different: they have different settings, characters, animations, gameplay options, art styles, simulation precisions, etc. Anyways, all these differences would not guarantee any of these games to be a high replay value game.

    Shooter Games

    Let's see where the PDG is hidden in shooter games. Obviously, it is in the shooting mechanics. Let's go point by point:

    1. Meaningful choices. Player is making informed decisions as he knows his HPs, how much health an armor adds, how much damage his weapon applies upon headshot or body shot. Choices have consequences. For example, when the player chooses to attack either he hits, and he gets closer to win condition, otherwise he might get hit and lose HPs.
    2. Dilemmatic choices. When a player starts an attack, he has a chance to hit the opponent, but also he has a chance to miss and expose himself for the opponent's attack. This is because he is out of cover and visible to the opponent, and the opponent has heard the shooting sound. The second dilemma is when the player tries to aim better, he needs to move less, which immediately makes him an easy target for the opponent. The third dilemma could be the headshot mechanics. In many shooters a headshot results in an instant kill, but body shots - don't. There is a triangularity here - headshot is a bigger reward (instant kill, better animation and sound effects, demoralization of the opponent player), but also it is more risky as the head is a smaller area to aim, and according to Fitts's law, it is harder and takes longer to aim [8]. Body shot is less risky, as the body has a larger area, but also gives a less reward.
    3. Unpredictable outcome. Here also, like in fighter games discussed above, before every shot the player cannot be sure that he will achieve his goal, and even with low HP it is possible to kill an opponent who has a full HP.

    Racing Games

    1. Meaningful choices. Player is making informed choices as the player knows what will happen when he presses one of four control buttons (accelerate, brake, steering left, steering right).  And obviously those four choices have consequences - real time consequences.
    2. Dilemmatic choices. In every racing game the dilemma is the speed vs control ratio. The more you have speed the less the control is.
    3. Unpredictable outcome. In a racing game it is possible to have a predictable outcome, when the player lacks behind too much, or he is way ahead of his opponents. In these cases the game becomes uninteresting. Therefore, usually Rubber Banding is implemented for Racing Games. By the way Rubber Banding term originated from racing games. Imagine as if the two vehicles were connected by a large rubber band [9].

    Economy Management Games

    These are the games like all incremental games, idle games, strategy games, games where the player needs to build an empire, a city, an economy, a character, a vehicle, etc.

    1. Meaningful choices. In these games there is a cost for every new item to purchase, build or upgrade. In the game menus you can find clear information about what the benefit of the purchase is.
    2. Dilemmatic choices. The dilemma is to decide where to invest obtained resources. Game designers implement conflicting choices or even if there is an optimal choice, the designer hides that fact carefully in order to create a perception of a dilemma. For example, the designer might make ChoiceA good at the start of the game, then ChoiceB may become dominant, and then again ChoiceA may become the optimal. The player needs to always check what choices he has. If there is no perception that choices are conflicting a game may still be interesting to complete once, but please take into account that PDG is for making high replay value games. Obvious optimal choices will break the feeling of player's agency - he will not feel smart by making decisions anymore. 
    3. Unpredictable outcome. In Economy Management games before every purchase or upgrade the player is not sure that he will achieve his goal. For example a player can't pass a level, because his vehicle or weapon has weak parameters. There are many upgrades that the player can do, and he knows each and every upgrade's cost and benefit in numbers. But the player is not sure that there is one particular upgrade that will guarantee him to win the level.


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