Yelling at the screen in frustration.
Consistency is vital. Its extremely important. Without it, your game has a large risk of becoming a horrible mess that prompts the player to abanbon your game very fast.
The lack of consistency manifests itself by the player not trusting the game. This happens, because the player notices that the game does something illogical, something unfair or cheaty.
Or just something plain ridiculous that makes you raise your arms and shout something inappropriate in frustration. I'm sure you've had a moment like that with a video game at least once.
That feeling when a video game pissed you off.
This eventually makes you stop playing the game altogether.
Why? Because no one likes it when they're being lied to. And this is what consistency is all about: Trust.
Good consistency ensures the trust of the player. When everything functions as it logically should, the player can safely have pure fun without thinking what stupid crap the game will pull off next.
Sure, there are games that do this and even as far as focus on this randomness specifically, but these are rarely those serious games that have endless potential and infinite gameplay. Such games are very shortlived anyway.
If you want longevity for your game, keep it consistent.
What is consistency?
Its about organizing the game and its mechanics that it all works seamlessly together as logically as possible. This makes the game feels natural. Everything makes sense.
Look at it this way: If you do X, Y will happen. If you jump, you will fly up into the air. If there is gravity, you will fall back down. You set fire to a piece of wood, it burns. You burn ice, it melts. You burn metal, it will get hot, but it wont catch on fire. A rubber ball hits a wall, it collides with it.
Its all about simple logical thinking, basic interaction and feedback of elements. This is what good consistency is all about.
If you give a player a character or object to control or interact with, make sure it has all the features you would expect from it logically. Atleast the very basics and don't limit it with cheap limitations or other illogical restrictions.
Consistency is important in everywhere. Both in story, gameplay, behaviour of objects, potential of what characters are capable of doing, environments, difficulty and so on.
What is inconsistency then?
Example: You are given to control a human. It makes sense that you can do all the following:
Walk, Run, Jump, Crouch, Climb, Look, Smell, Eat, Hear and Interact with solid objects using your body. Its all part of being a human, after all.
It doesn't make sense if you lack all or some these features. Wouldn't it feel strange if there was small rock in your way and you can't jump on it or climb over it? Or if there was a ladder or a door in the world that you can't climb or open?
That is a lack of consistency right there. You were given a human to control, as the game claims, so its obvious you should be able to do those actions, but if you can't, then the game is fraud and unfair. You're being lied to. Its a harsh analogy, but thats the most direct way to explain it.
Lack of consistency in a nutshell.
This logic applies to everything, not just this example of a human. Be it a world, story, a mechanic or behaviour of objects and characters. It all matters how it behaves.
When something doesn't work as it would by logic, the player will becomed distanced from the game, the immersion breaks and the player can't properly enjoy the game as he can't trust it. While the player might try enjoy the other parts of the game, the damage has already been done.
Knowing the game has failed him or her, the player takes note of this and begins to think outside the box to anticipate more suprises like this. This initiates a metagame between the player and the game itself that destroys any immersion you had going on.
Consistency, who needs that? Screw logic.
It defocuses the player from the most important part of the game; enjoy it for what it is.
As to prevent this from ever happening, you need to get it done right from the very beginning and avoid ruining the game with inconsistencies and other logical failures by organizing the system and its element in a consistent manner.
You do this by simply making sure anything you add to the game makes sense.
To help with it, a strong framework is needed that begins from bottom to top, starting with a well established set of rules by how your universe behaves and then how the items behave by those rules and finally how characters interact with the world, the items and each other.
This builds consistency naturally into your design.
Spawning and origin; the clown car effect.
One very infamous element of bad design is in spawning and creation of things.
If you've ever played games where you have to fight enemies of any kind, you might remember that there are instances where monsters are spawned out of thin air, teleported in your face or appear suddenly behind the corner without any source or reason what so ever.
This is even worse when the said monsters are being spawned endlessly or respawn five seconds later after being defeated. This is probably one of the worst inconsistencies you can ever have in any game. Especially if its based in a real-life setting.
Its like fighting a war against endless, self-reproducing robots that teleport in you face.
Not only its unfair, but its ridiculous and illogical as well. It feels frustrating and futile.
They just keep coming over and over again.
Everything needs and has a beginning. Everything has an origin from where it comes. This applies to every part of the game too. World, characters, items, monsters, story... all of it has an origin, a beginning.
Always think where something comes from before you put it there. Make sure the player will be aware and understand this origin during the game too.
Also, If you really have to spawn something out of thin air, at the very least, apply a limit to how many can spawn and inform the player about it, or he will get frustrated. Always be fair to the player, keep his trust up and never lie to him.
Player trust and consistency is key to a good game.
Okay, that may have sounded like its something out of quantum science, but don't worry, all it means is that a scripted story does goes against the game mechanics.
As in, the game's story tells you something, but it doesn't really happen or does the opposite.
This is a huge problem with video games that are completely built around a scripted storyline. The reason is that games are an interactive media, while scripted storylines are a passive media.
A game has you actively do something to progress, but a story only needs to be listened to. When you try to combine a game and an active story, which you as a player are put in as a central part of as if it was a movie, you're trying to put a square peg in a hole.
They simply don't connect.
A player is a human being with his own free will and forcing a scripted personality on the player character isn't going to work. Unless you brainwash him into a mindless slave, that is. But the point is the player only does what he wants to.
A better way of implementing a story in a game is to make the story completely passive and allow the player to be himself and react to the story as he wants to.
By a passive story, I mean instead of doing this:
You are a puppeteer, not the actual character.
"You are the chosen one Igor the Magnificent. Your destiny is to slay the demon king"
You do this:
You are you, as a hero. This is your story.
"You are a human in a land of turmoil ravaged by a demon king, things are looking desperate."
"You may slay the demon king, ally with him or become one yourself. Or just dick around. Up to you. Have fun."
This is a much more natural alternative when you allow the player to be him or herself and make their own story by going to defeat or ally with the demon king. It becomes a more personal experience and thus heaps more enjoyable than if you were forced into a scripted linear quest by being someone you're not.