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  • Replayability: Game Mechanics As Periodic Dilemma Generators

    - Narek Aghekyan

  • Considering player's skills and perception 

    As I have mentioned earlier, projecting PDGs abstract concepts onto games is only one part of the job. The last part is to consider the player's skills and psychology. The player needs to perceive that the game is acting like a PDG. If technically the game is a PDG but the player fails to perceive it that way, then the interest will be lost. Here are some notes that we need to consider while applying PDG when designing a game:

    1. Meaningful Goals. The game designer cannot set an arbitrary goal in a game and hope that the player will care for achieving that goal. Also the designer cannot hope that the player will create meaningful goals for himself. For example, the designer cannot think that he will create a shooter game without an explicit goal and hope, that the player will define his goals by himself. You, as a designer cannot expect that the player will set goals such as advancing through the level by killing all enemies, or play so that the player will be unnoticed by enemies. The correct way of doing this is to create a conflict in a game which immediately challenges the player. E.g. in a runner game put enemies in front of the player so that they are able to kill the player. In this case the player will have to deal with those challenges. And he will define goals for himself like the ones mentioned above and those goals will already be both meaningful and interesting to achieve for the player.
    2. Achievable and clear goal. First of all, every game needs to have a clear goal. Activities that do not have a clear goal, are chaotic and do not result in Flow experience [11]. So make sure in your game the player clearly knows his goal. The player not only needs to have a clear goal, but also needs to believe that he can achieve his goal.
    3. Informed choice. Based on the player's skills, the player perceives different available choices. The player can expand his choices by expanding his skills. Even if the choice is perceived as available, it is a matter of skill or luck to execute the choice and to get the benefit of that particular choice by paying the corresponding cost.
    4. Choice consequences. Even if the choice taken has had an actual consequence, but the player didn't perceive it, then the choice will not be perceived as meaningful. In order to get a feeling of Flow there should be a clear and fast feedback for every action [11]. Missing a consequence is the same as not getting a feedback for a taken choice.
    5. Dilemmatic choices. Here again the player's perception is playing a significant role. If technically there is an optimal choice, but the player is unaware of that opportunity, then he might perceive the situation as dilemmatic and enjoy the game.
    6. Unpredictable outcome. If players perceive that the game's outcome is unpredictable they will continue to play. This is a typical case, when a good chess player plays with a bad chess player. At some point for the good player it is obvious that he has won, but the bad player still continues to play, as he does not have the same perception, and the game is still interesting for him.
    7. Player Skill or Competence - Over time the player learns that even though in every situation he faces a dilemma, he will find situational patterns, where one choice is typically better than the other choices [12]. In these situations the player will feel himself in a less dilemmatic state. In other words, he will become skillful and will feel competent, which is good. But when the player will become so much competent that the game outcome will become predictable, then the perception of PDG will be lost and the interest will be lost too. There will be no replay value left in that game for that particular player.
    8. Safe to fail - When situations are dilemmatic, it is harder to blame a player for his failure, as he always can argue back, that the other options had drawbacks, whereas in situations when there is a clear optimal choice, the player is feeling more "unsafe" to make decisions.
    9. Puzzles - Based on my definition of a replayable game, choices should be dilemmatic. But puzzles are games that usually have optimal choices and usually have only one win condition. Therefore, puzzles have low replay value. You cannot collect the same Jigsaw Puzzle 10 times in a row, and feel fun, but you can play 1000 rounds of SimCity, CS:GO, DOTA or Chess and still have fun. This is why we cannot make games that are fun to play and teach players to science. Probably, this was the reason why Chris Crawford's has made his famous Dragon Speech and left the industry. [13] Science is not about dilemmas, it is about optimal choices - science is a puzzle for humanity to solve. Therefore, once it is solved, it is not interesting to replay, and after that it is not Safe to fail.
    10. Self-expression or Autonomy - Because the player is in dilemmatic situations, which means there is no optimal choice, this means that every player will take choices that express their own type of personality. There is no optimal choice, therefore some people will usually play safe (because they are that kind of people in life too), other players will play in a risky way, etc. They will feel autonomy to choose their own sub-goals, their own way of playing the game, their own way of expressing themselves. (Please compare with the thoughts from Steve Swink mentioned in the Introduction.) Playing a game becomes a self expression like an art. And on the other hand, this means that the game designer is not forcing the player the sub-goals he has prepared for the game. The player does not feel that he is obligated to do something, the player feels that he does what he wants to, and during the game, he can change and adapt his sub-goals too. He is free to choose, and none of the choices are wrong. Just over time he will recognize the patterns of situations when some solutions typically work better, he will become skillful, as mentioned above. And even in that situation he will choose to be competent or not - maybe he will feel that he needs to experiment new approaches.
    11. PDG is a perception. In his book Csikszentmihalyi writes "Enjoyment does not depend on what you do but rather on how you do it." [11] He writes how some activities are very good for inducing Flow state, and others are not. But even in very uncomfortable states, Flow conditions can be satisfied and the person can experience the Flow state. The same is true for PDG systems. The same system can be perceived as PDG for one person, and non-PDG for another. But there are systems that are very good at being perceived as PDGs - for example Football or Chess games, and others that are not good at that e.g. Rubik's Cube. But it does not mean that it is not possible to perceive Rubik's Cube as a PDG and it is not a must to expect everyone to perceive Football as a PDG.
    12. Aesthetic, religious, taste issues. People may not want to try a system for some reason, hence will not be able to feel its PDG properties. Another reason is that people can have some aesthetic, religious or other reasons not even to try an experience to even be able to feel whether it is a PDG or not. For example, one of my friends hates Brazilian jiu-jitsu (BJJ) for aesthetic reasons (a man hugging and rolling another sweaty man on the ground), but BJJ is a really Periodic Dilemma Generation machine - imagine like a real time Chess instead of currently played turn based one. Other people might not want to play a shooter game for religious reasons.

    Summarizing this section we can conclude that the perception of PDG is highly dependent on a player:

    1. The same game, even the same situation can be perceived as a PDG by one player and a non-PDG for another one.
    2. The same situation in a game can be perceived as a PDG initially, then after playing and getting some skills the game might feel like a non-PDG for the same player.
    3. The same game can provide PDG experience at some moments of the play, and stop acting like a PDG at other moments to the same player.

    PDG as a tool for a game designer

    Please note that PDG is just a tool in the hands of a game designer. In spite of providing an abstract concept as a tool for designing games, we should not forget that creating a game is an art. There are no strict recipes, and every designer should use his intuition to understand when and how to use the tool. For example, a designer should decide what the dilemma generation period is. For one game it might be every second, for another game it might be every minute. The dilemma generation period might change during the game. Also how critical should be the consequences of the player decisions, should consequences be long term, or short term? There are many things that the designer needs to adjust for a particular game. But not implementing any PDG in a game might be a good reason to obtain boring and low replay value games.

    PDG is also very helpful when you want to work on a new game idea. When you want to design a new game (if you are a HC game developer, then you need to make several games per month) you always have a question on what game to make so that it is fun to play. But by using PDG it is possible to transform the question to the following. Consider a PDG that works in some specific way, i.e. we have already an interesting system. So what are the design details of this system? For example, I design a PDG the following way: I have different paths, every path enables a different speed. The one that has a higher speed is also more dangerous to travel in. For this PDG the game designer needs to come up with a game design details (needs to do the detailed design of the system) so that the properties of the PDG mentioned lately will be satisfied and the metaphor of the game will make sense to the player. This is a totally different approach. Compare again:

    1. What game to make so that it will be fun to play? (There is no certainty or something to start with, right?)
    2. How do I design a system that implements the properties of a certain PDG? (This is certain, this is more like a clear task for a designer to start to work on.)

    You might ask: "How should I come up with a PDG idea?" I think you would agree that this is much-much easier than "coming up with a game idea that is fun". Also you can reuse existing PDGs in different contexts and you will obtain different games.

    Final Thoughts

    It might be argued that this definition of replayable games is useless and does not express players' taste as we have seen many repetitive games in AppStore's top charts. For example, Pack MasterDentist Bling both reached top #1 in the "US Games" category of AppStore and many other games that have very repetitive gameplays too. Aren't they replayable games, don't they have good retention values? No, those are not high retention games! Sounds paradoxical? Yes, it does. And it took years of experience for our team to understand this mystical truth. If a game is not a good one, what is the motivation to spend a significant amount of money on UA and bring it to the top charts? There are two explanations for this:

    1. The HC game publisher could find a very marketable but very repetitive gameplay, which means that both CPI and retention are low. This means that it is possible to obtain positive ROI not because of high LTV but because of low CPI. For example, compare Game1 with CPI $0.18, and average LTV $0.65 and Game2 with CPI $0.05 and LTV of $0.19. Some publishers call these low ROI games Ultra-casual and are OK to publish them, others are not interested in publishing positive ROI Ultra-casual games because of very low margins.
    2. There is fierce competition between publishers in the HC market. Newer or smaller publishers need to demonstrate to game development studios their capabilities. They need numbers such as N downloads, M top games published, etc to tell studios how powerful and successful they are. Therefore, they might even take games with ROI ≤ 0% and push to the top charts. (Fake it till you make it?) By the way, in such deals, studios might get no payouts or very small payouts. 

    Thus, reaching AppStore tops and/or getting millions of downloads neither means a game is commercially successful nor it means the game is good at all. And this is not specific to the HC genre. Therefore, as a side-note, game development studios need to pick games as references and publishers as partners very carefully.

    There can be other seeming problems related to the concepts discussed above. In his GDC 2012 talk titled "Sid Meier's Interesting Decisions" Sid Meier says that his "series of interesting decisions" are criticized for example on Guitar Hero and Jigsaw Puzzle as these games don't present interesting decisions, but they are fun to play. [2] For the same reasons it might be attempted to criticize the replayable game definition written above. The following thoughts are meant to clarify that potential criticism:

    1. We should consider Guitar Hero not a game but a musical instrument. The operation principles of Guitar Hero are no different from real guitar playing. It is clear that it might be really fun to play piano piece or run 1000 meter distance over and over again, but the reasons, mechanisms of this experience should not be discussed in the context of games. This is well covered by the concept of the Flow [11].
    2. All puzzles are very low replay value experiences, as they have optimal solutions and have predictable outcomes, especially if the solution is already known. 
    3. There are video games that are awesome games but are not replayable, e.g. Far Cry, Tomb Raider, The Last of Us, etc. They might be very enjoyable single time experiences. One might even replay the full game 5 times, but no one will play it for 1000 times, and equally enjoy the game, whereas you can play Chess, DOTA, CS:GO, Mortal Kombat as much as you wish and even enjoy more than the first sessions. For example Journey by Jenova Chen is an amazing game, it is an art, but by the definition above it is not a replayable game. It does not have a significant replay value. It is more like an interactive animated movie. These types of games are out of scope of this article since we discuss high replay value games.


    An abstract concept of Periodical Dilemma Generator (PDG) is defined. We state that high replayability games have one or more PDG systems built into the game. Moreover, there is a hypothesis that having a PDG is a necessary and sufficient condition for a game's replayability. Of course, this is true, if there is a corresponding player perception about the system's PDG properties. PDGs are good tools for analyzing or making high replay value games, if the designer understands the tool and finds a good approach how to use it. Several games or game genres are analyzed to show how PDGs work and where the PDG should be implemented. It is clear from those examples that the replayability is usually the virtue of the core mechanics and the replayability can be achieved without adding new characters, weapons, levels or a meta-game into games. From the discussion above it is straightforward that all the conclusions are directly applicable on literally any genre of games.


    1. Game Feel: A Game Designer's Guide to Virtual Sensation by Steve Swink, 2008
    2. GDC 2012, Interesting Decisions by Sid Meier
    3. Game Design Workshop: A Playcentric Approach to Creating Innovative Games, Fourth Edition by Tracy Fullerton, 2018 (Chapter 11, Improving Player Choices)
    4. Replay Value Wiki
    5. Game Mechanics: Advanced Game Design by Ernest Adams and Joris Dormans, 2012
    6. The mighty MMM concept in hyper-casual game design, 2019
    7. The Art of Game Design: A Book of Lenses by Jesse Schell, 2nd edition, 2015
    8. Fitts's Law Wiki
    9. Rubber Banding Wiki
    10. The Math of Idle Games Part I
    11. Flow: The Psychology of Optimal Experience by Mihaly Csikszentmihalyi, 2008
    12. Theory of Fun for Game Design by Raph Koster 2013
    13. GDC Founder Chris Crawford's Dragon Speech


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