The first element of analysis is to consider rhythm. With rhythm, you expect the recurrence of a pattern in consistent intervals. So in other words, pacing is defined by "what you expect to come next".
In concrete terms, let's consider a typical puzzle game flow. You begin a level and are introduced a new mechanic. The puzzle with this mechanic is simple and flexible. The level is short. In the next level, the difficulty ramps up a bit, continuing until the pattern repeats and another mechanic is introduced. A sense of pace and flow is created by the repetition of the pattern by which new mechanics are introduced to the player. What if the third mechanic was introduced without any easing in of difficulty, and the player simply couldn't solve the puzzle?
Identifying Types of Pace
If the game sets its pace properly and hits all the right notes for the player it will probably feel very satisfying and smooth. The game will infer to the player, "this is what you're going to get", then gives it to them. The player knows what they are to be given, and they are given it. This is a smooth experience.
However, now let's assume the game throws something at the player which they do not expect. A sudden plot twist, maybe an unwarranted intervention of a puzzle which halts the progression of a level.(by which consistant progression was previously expected) In this case, the rhythm is broken, so it's going to feel jarring and harsh. This might discourage players. Imagine if you're listening to a song and it suddenly shifts, without warrant, from a 160 tempo dubstep mix to a 110 tempo folk track. "This isn't what I wanted, this isn't what I was expecting," the player might think to themselves. This is a discordant experience, where the expectations don't match the outcome and the sense of rhythm is broken.
Analyzing the Sense of Pace
We've established what pace is, that it's something predictable in the game's flow, so now I'm going to extend that, let's use some graphs to demonstrate this.
Let's imagine the x-axis is time and the y-axis is the general progression of the game.
What they have in common is that, even if their pace isn't constant it is consistent and predictable, save for one.
Look at Fig. 3, which has a sudden shift in the pace of the game, I've graphically illustrated a discordant shift in the game's experience. It's a point of change that isn't predictable beforehand.
I want to make a departure from mathematical explanations now, though, and we'll continue this speaking in more direct terms. However, I believe thinking about pace in terms of a graph is an excellent way to demonstrate a simple understanding of it.
Imagine a song with no variations, no shifts in tone, rhythm, nothing whatsoever. That would be boring, right? If things were homogenous all throughout your experience would probably feel watered down.
This comes, I believe, from never changing the player's expectations. Once something can become patternized and repeated without consideration it is no longer interesting--This is a particularly important consideration for a game designer where the game has a constant set of mechanics.
For instance, imagine an RPG where there was only one set of skills--no progression. Imagine Pokemon where there were only three creatures, and you could only have one in your team. It would feel stale! By continually introducing new concepts there remains points of interest for the player to act on.
Now I'm going to extend what we talked about previously. What if a game consistently introduced new points of interest? In other words, the pace of introducing new concepts.
I would consider this a "stable pace", because the game (should) remains consistently interesting.
Except there's a danger, the same danger: something that can be identified to a pattern is not interesting, just as we discussed before. If the player expects a steady stream of new content all throughout the game, and I do mean steady, is it really that interesting? A major source of excitement is in pleasant surprises, no? Now I want to develop that idea.
Keeping Things Interesting Without Discord
If you haven't noticed the ironic element yet, I'll just throw it out there right now: pacing is the rhythm by which the player expects things to come, yet, if you keep playing the same rhythm it gets boring. That is, if you only give the player what they expect, they get bored.
And now I'm going to rock your world, by telling you to be unpredictable. Yep, just did it, it's out there. My hands are in the air, take me to jail. I told you earlier to be predictable, now I'm saying the opposite. The jig is up, right? Right.
Wrong. By establishing what is effectively the tone of your game, you're telling the player "this is what you're getting in my game", a fighting game is quick to set the tone to say "you're getting intricate fighting mechanics bundled tightly, and not much more", an RPG says "you're about to go on an epic journey where you'll see new things, meet new people, and become the strongest swinging dick in the land."
At that point, it's up to you as a designer to deliver on that. Doing otherwise is the discord we talked about earlier, where you went against what the player expected out of your game. Now we're doing mixups, by going against how the player expects the game to progress. We are evolving their sense of the game and its pacing by changing the pacing, yet keeping it within the same bounds of expectations as established initially.
A large part of this is what I affectionately refer to as "breaking the horizon", and my buddy Alexander Martin(AKA Droqen) wrote an excellent article on it a while back. I'm going to rock your world and tell you to go read that, read it right now, before continuing this article. Sorry to break your pacing.
With these mixups you are expanding what the player considered they could get out of your game.
Utilizing The Sense of Pace
*gasps for air*
Okay, we're concluding now. You've came with me a long way, so I'm going to try to wrap things up for you in a neat little package now.
Pacing is the rhythm by which your game flows, bounded by the expectations you set for the player by establishing a tone. A smooth pacing is one which consistently delivers on what is expected, and a discordant pacing is one which fails to do so. A stale pace is one which becomes boring due to a lack of pacing an introduction of new content. A stable pace is one which overcomes the flaws of the stale pace, yet has the danger of becoming boring by never mixing up its own pace of content flow. Breaking horizons keeps your game interesting by offering something both pleasant and unexpected.
I'm not going to tell you how to utilize pacing, though. That's up to you. Be crazy, be experimental, or maybe just go make a solid experience. I do encourage you, though, to keep these things in mind the next time you're playing a game, and watch carefully for the various aspects of pacing present in the game, how they're mixed up, and how they either succeed or fail to deliver on their promises to you.
Until next time, ciao.