Well, I figure as long as this forum says "Game Design" I might as well throw in a game design topic or two. If I actually finish what I start, I hope to gradually cover several topics in such a way as to be a useful reference.
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TOPIC: Autonomy, Competence, Relatedness
PRACTICAL APPLICATIONS: These are used to make a game more compulsive and compelling. In psychology labs, they are statistically more effective than any other measure at getting people to keep playing a game. MMO developers and makers of Facebook games have put particular emphasis on these above everything else. (Most likely you won't want to go that extreme, but these are still handy design tools).
REFERENCES: These are pretty hot topics right now, so...there's lots.
This one goes into a lot of good detail about the theory:
http://www.jonselin.com/uploads/Immersyve%20SRigby%20Talk_AGDC%202007.pdfThis has extremely little detail, but it's a TED talk and thus automatically entertaining:
http://www.ted.com/talks/dan_pink_on_motivation.htmlBits and pieces of it have even hit classical news sources
http://www.guardian.co.uk/technology/2011/may/15/video-game-design-psychology-----------------------
The theory holds that motivation in the human brain is driven by three fundamental needs. Competence (feeling like you're capable), Autonomy (feeling like you have choices), and Relatedness (receiving recognition from others).
COMPETENCE:
How often is the player's intended action the actual outcome?
How quickly do players feel they're on top of the in-game mechanics? The in-game controls?
This extends to "my avatar was walking in a 3D space and fell off a cliff". This extends to "I'm playing Portal 2, and it really looks like I should be able to make a portal on that wall, but I can't. Screw this game!"
And yes, to be honest, the simpler and easier your game, the better you're likely to do on competence.
Examples of non-Competence:
Final Fantasy Tactics is a big offender here. You need to use L and R keys to insert characters into the fight, which is non-obvious. It's a 3/4 perspective where it's not clear which direction of the D-pad corresponds to which diagonal axis. It throws a preponderance of mechanics at new players, and forces them to use many of them (like setting your orientation after you move--it's not like this is an optional extra that experts can turn on; even a brand new player has to do this after every move).
Note that different audiences are going to come in with different prior competencies. For a fun example, I've heard it argued that if the Atari E.T. were released five years later, it would have been considered not that bad. What E.T. did was context sensitive actions (i.e. "A button opens doors, talks, extends E.T.'s neck, uses tape recorder, etc depending on E.T.'s location") which at the time was horrifying inexplicable madness--no one could understand these controls!
AUTONOMY:
Players feeling like they have real choice. Not only that, but that they are the cause of their actions. (As opposed to, say, "I stepped forward and was entered into a cutscene where the main character punched the boss"). And measurably, the number of different game objects you can interact with (including levers, treasure chests, NPCs), the number of different modes of gameplay you can go into. (This is why GTA offers 50 dumb minigames rather than doing one thing very well).
Examples of non-Autonomy
I'm going to skip the obvious "games with lots of FMV and forced linear paths without customization" examples, and jump straight to Portal. (minor spoilers). In Portal, there's a scene where GLaDOS forces you to do something that you emotionally really doesn't want to do--destroy an inanimate cube to which the player has grown attached. There's no alternate path; no sidequest you can embark on to delay the inevitable, you're just forced to do it. And this is actually brilliant design--taking away player autonomy makes the player upset, but it is framed in such a way that the anger is focused towards the villain, not the game designer.
RELATEDNESS:
Humans are wired to seek recognition and connection with others. The good news for everyone working on single-player games is that this stimulus can be faked with NPCs (often more consistently than real humans, because NPCs will be more consistently grateful and positive than a random 14-year-old on the internet). Statistically, people respond better to positive feedback, than to belittling feedback (so in Katamary Damacy, the King of All Cosmos telling you your efforts are pathetic when you complete a level may have been part of why the game never got that large in popularity).
Examples of non-Relatedness
I'm just picturing "Super Luigi RPG" here, where you walk up to NPCs and they say "I'm sorry, what was your name again?" You stop a volcano from destroying an entire town, go talk to the townspeople, and they're like "Hey, did you hear? Mario saved a kitten out of a tree! The poor kitten couldn't climb down...." You perform a super ultimate charged crouching jump, and some kid says "That's not impressive. Mario can jump way higher! That's why Mario's a hero!"
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Note that there isn't necessarily an automatic right-answer to any of these. I mean, there is if you want to make people compulsively return to your game without understanding why they like wasting time playing it. But in a forum about made-for-fun ROM hacks, that's not necessarily the goal....