[In this in-depth article, veteran designer Davies looks at games from Call Of Duty 4 through Dead Space to analyze the art of game level pacing.]

Introduction

"Pacing" is a word bandied around a lot when talking about level design, but it is actually a very complex concept to pin down. Just how does the pace affect the player's perception of the level and what is it that sets a well paced level apart from a poorly paced one?

The Fundamentals

With these questions ringing in my ears I was determined to try and delve a little deeper into just what constitutes level pacing, but I found very little literature on the subject. Instead I decided to focus my efforts on breaking down the core elements of what determines pace itself.

In doing so I identified several key aspects of game pace:

• Movement Impetus -- the will of the player to move through the level.
• Threat -- the notion of danger.
• Tension -- the atmosphere and mood of the level or perceived danger which is reflected in the player.
• Tempo -- the level of actual action currently being experienced by the player.

Movement Impetus

Movement impetus is the will or desire of a player to move forwards through a level. There are several ways in which the player can be pushed into moving or stalled from pushing forwards in order to affect the movement impetus and thus the pace of the action.

There are many elements that increase impetus to move:

• Introduce a threat from behind -- as long as the threat is significant it will cause the player to want to move away from it.
• Present an objective ahead -- dangling the carrot is one of the most effective methods of encouraging movement. A clearly defined goal is vital in creating this urge to follow it.
• Impose a time limit -- quite obviously the restriction of a time limit will encourage the player to not hang around. Too many imposed time limits can be extremely frustrating however.
• Narrow physical options -- limiting the space in which to travel -- i.e. long corridors as opposed to open spaces, limits the amount of choice available to the player and in turn increases the speed at which they tend to move.
• Draw the eye -- items of interest will pull the player towards them. Judicious use of these will help to pull the player through parts of the level. Bear in mind that once they reach the item of interest they are likely to pause at that point.
• Architectural pressure -- specific forms of architecture promote movement. Walls that angle down, long corridors, junctions, etc all have psychological impact upon the player.
• Snatch desired object -- taking away a desired object will often trigger the player into chasing after it.
• NPC leads the way -- having a third party lead the player though the level will nearly always directly affect the movement impetus.

Continual movement keeps the tempo high, but it is undesirable in many ways. Often players want time to take stock, catch their breath, formulate a plan or even just soak up the atmosphere -- it provides a break from constant travel. Also in production terms continual travel often requires much more real estate in which to move -- this is both a production risk and possibly a technical issue.

Conversely there are also many elements that decrease impetus to move:

• Wow moments -- stunning scenery, dramatic actions, impressive vistas or other elements that halt the player for a while.
• Obstacle -- something blocking the progress ahead will decrease movement impetus and force the player to find a way around or a way to clear the blockage.
• Altered movement -- a different movement method may require more thought, such as scaling walls via handholds.
• Introducing a threat ahead -- a group of enemies ahead, a flaming pit or any other potential threat will slow the player whilst they plan to deal with it, then execute said plan.
• Increased tension -- when tension is particularly high (usually through a high perceived threat and good atmosphere) then the player will often be fearful of moving quickly. Dead Space is a classic example of this -- many players tend to move slowly to ready themselves for sudden attacks.
• Multiple Routes / Open World -- choice requires thought and thought slows movement impetus. Multiple routes and open world games offer a plethora of choice. Perhaps the ultimate example of slowed impetus is the moment when a player exits the sewer in Oblivion and sees the huge expanse of the world before them. It takes a moment or two just to take it all in.
• NPC halts player -- just as an NPC can lead the player, they can also halt the player or slow them down.
• Taking stock of inventory (collecting items) -- whenever a player encounters an item they are likely to slow down to investigate. Complex inventory systems will also require management that will slow movement impetus. Further still -- having collectible items in the first place will encourage exploration.
• Dialog / Roleplay -- moments of dialog with NPCs or getting into the character will generally require more involvement from the player, and will thus slow movement impetus.
• Story exposition -- generally the exposition of story will require the player's attention and will thus slow movement impetus.

Constantly slowing movement impetus can also be dangerous, as it can prevent the player having a feeling of progression. A balance needs to be struck in providing a sense of movement and accomplishment and allowing the player time to themselves to explore, soak in the atmosphere or to take stock of their situation.

Threat (Actual Danger)

The pace of the game can also be increased by the sense of peril that is experience by the player. The more threat the player believes they are under, the quicker their pulse, the more nervous and often more panicked them are.

Threat can come in many forms -- each form having a different feel of pacing. For example combat tends to be more frantic and higher paced than traversing an environment, even though the end result -- death -- could potentially occur in either situation.

Generally the level of threat felt by the player is determined by whether the threat is being caused by an external force -- an enemy, an encroaching hazard, etc, or whether is a danger that will result from the player's own mistake. Threats from external forces tend to have a much higher level of pace than those that will result from a player's mistake, as they have time to gather their thoughts and create a plan when they have control.

Proximity of a threat also has a huge influence on the feel of the threat. An enemy at a distance is not nearly as threatening as one very close by. This is something that stealth based games can really use to their advantage (and is something that can also build a great sense of tension).

Adding a time limit to a task automatically increases the level of actual danger, as the control the player has over the game world has been reduced -- there are now limits placed upon them which can induce a level of panic.