Design Elements

Action games are a good source of distinct design elements, mainly because their relative simplicity makes analysis of their game mechanics fairly easy compared to the more complex genres.

What we are attempting to do when we are extracting design elements from games on a genre-by-genre basis is to form the basis of a genre -describing "meta-game." What we mean by meta-game is a description of an archetypal action game. Of course, such a construct is purely hypothetical. It would be pretty much impossible to actually produce a fully comprehensive document. So with this in mind, let's start with an analysis of the design elements that govern the rules of the game. These design elements are only a small subset of the whole, but the aim is to give a starting point for your own investigations into the gameplay mechanics of action games.

The Rules

The rules of an action game describe the basic game mechanics. They are usually very simple because of the frenetic nature of the gameplay. Fundamentally, action games are games that require skill as the primary factor for play, not rote memorization of complex rules.

There are many design elements that we can examine here, and the following few sections will cover some of these. Note that words in bold indicate references to other design elements within this chapter.

Levels

Action games are often split into a succession of levels. A level is a specifically defined area in the game arena, in which the objective for the player is to complete a specific task. When the task is finished, the level is complete. Each level is played until complete, and upon completion the player's avatar is moved to the next level, and play continues. Generally , the difficulty will increase with each subsequent level.

Often, levels are grouped by theme. All the themed levels in the set will have a similar appearance and set of enemies. A set of themed levels usually ends with an encounter with a big boss . In some cases, the boss has to be defeated with the use of power-ups and/or skills that the player gained during the preceding level set.

Checkpoints

If the nature of the game is such that the player progresses through a level, then the position that the player's avatar appears in after a life has been lost is often determined by the use of checkpoints.

The most straightforward form of checkpoint is that the avatar appears in the same location where it died, or in the case where that is impossible (for example, Mario falling into water), then it appears in the last safe location before it died (for example, the last platform that Mario was on before he fell in the water). The state of the level is unchanged ”the avatar just reincarnates, and play continues.

Other (more difficult) games, such as Space Tripper , simply restart the level from the beginning upon avatar death. This particular form is fairly rare, because it increases the game challenge significantly, and often causes player frustration. It requires that the player play a "perfect" level in order to progress to the next one.

The final form of this design element is an amalgam between the first two. As the player progresses through the level, he reaches a number of predefined checkpoints. When the avatar dies, the level is reset to the last checkpoint that the player successfully achieved. An example of a classic game that uses this form is Moon Patrol , shown in Figure 9.9.

Figure 9.9. Moon Patrol.

Lives

The player's avatar is usually given a small number of reprieves from death. Initially, the number of lives provided usually ranges from between three and five. A life is lost by collision with an enemy or some other dangerous structure. Extra lives can be earned either by picking up a power-up or reaching a certain score threshold multiple. The player's avatar is usually invulnerable for a few seconds when reappearing after losing a life, in order for the player to gather his bearings. When all lives are lost, the game is over.

Often, this design element appears in conjunction with the energy design element. If this occurs, then the avatar isn't destroyed immediately on contact with the enemy. Instead, energy is drained from the avatar. When all the energy is drained, a life is lost. When all lives are lost, the game is over.

Energy

The player's avatar is given a limited amount of energy, some of which is depleted when the avatar is injured. It can often be partially, or even fully, replenished by the use of a collectible or a power-up . When the avatar's energy is depleted, the game is over.

This design element is sometimes used in conjunction with the lives design element. In this case, when the avatar's energy is depleted, one of the lives are lost. Sometimes the energy is spread over a number of physical features ”for example, it can be a limited resource that is shuffled between shields and fuel, requiring the player to carefully balance resources.

Time Limit

The time limit design element is indicated by the use of a timer that counts down from some initial value to zero. When the timer reaches zero, an action occurs that causes a major event in the game.

The time limit is normally used in one of three ways. The first way is as a level timer. The player has a limited amount of time to complete the level, and if he fails to do so, the level is reset, and the player has to start again. Often, this is accompanied by a life loss and, if the level is finished with time left over, then this excess time is multiplied by a constant as a score bonus.

The second use of the time limit design element is as the countdown to a catastrophe. The player has to achieve some task before the timer runs out, or the task will become much more difficult to achieve. This particular form is used in Sinistar . When the timer runs out, it means that the eponymous Sinistar has been built, and the player is in a lot of trouble.

The third use of the time limit design element is to limit the effectiveness of power-ups . When the timer runs out, the temporary power-up that it governed is removed, and the player's avatar reverts to the normal state. Pac-Man's power pellets, which allow the Pac-Man to eat the ghosts for a limited time, are good examples of this form.

Score

One feature that is often specific to action games is the score indicator. Often in an action game, the only indicator of progress is a score. It is how the player is intended to measure her success against others. Many types of games do not use the score pattern, but action games are pretty much centered around it.

Scores are recorded in high-score tables for posterity, and to provide bragging rights for the very best players. Many games also reward skillful play with bonus scores and multipliers. The classic example of the score multiplier in action can be found in Pac-Man : After getting the power pill, the first ghost eaten earns 200 points, the next earns 400 points, then 800, and then 1600 respectively. Hence, skillful play is rewarded with higher and higher scores.

Power-Ups

One of the staple design elements of action games is the power-up. As a reward for progress, the player is given the opportunity to increase the strength of his avatar. In the case of a shooter, this can come in the form of stronger weapons or shields.

Power-ups come in two main strains: permanent and temporary. A permanent power-up is one that remains with the avatar for the remainder of the game (or at least the current life or level). Space Tripper (and many other shoot 'em-ups) uses this model. Space Tripper is unique, however, in that when the avatar dies, only power-ups gained on that level are lost.

Temporary power-ups are usually short lived (anything from a few seconds up to a couple of minutes) and provide the avatar with a powerful advantage for a short time (such as shields). The general rule is that the more powerful the advantage, the shorter the time it is available for. The Quad Damage power-up in Quake III is a perfect example of this. An alternative to the time limit is to allow a certain amount of usage. For example, shields may be used up after they are powered on for a certain period of time, or after a certain number of hits.

One interesting aspect of power-ups that is used in quite a few games is the concept of power points. The player is awarded a certain number of "points" to spend on an upgrade, and then to a certain degree, the player is allowed to decide how he wants to upgrade his avatar. Space Tripper has two main weapons; the weapon that is currently selected is the one that is upgraded. Successful play requires that the player balance the upgrade points between both weapons.

A specialized case of the power-up is the combo move . This is more often found in fighting games, and is a power-up that relies on the skill of the player to execute a sequence of commands with exact timing. The reward for success is a special move that devastates the opponent 's defenses. The effectiveness of the move is often related to the difficulty of execution ”a period of time in which the avatar is open to attack. Thus, more difficult combos carry higher risk.

Collectibles

Collectibles are bonus objects that allow the player to augment his score. They are not essential to the game, and are often used just to augment the player's score. The player is not penalized for failing to collect them, but if he can justify the risk, then the rewards are high.

In some cases, collectibles can unlock secret levels or cause special bonus events. For example, in Rainbow Islands , one means by which the player could kill enemies was by collapsing rainbows onto them. Enemies killed in this fashion deposited crystals that could be collected for bonus points. If these crystals were collected in the right order (red, orange, yellow, green, blue, indigo, violet ), then a doorway to a secret level would be opened, which gave the player a huge score and a permanent secret power-up .

Smart Bombs

Defender was the first game to introduce the concept of the smart bomb (see Figure 9.10). Smart bombs are used to get the player out of a difficult situation when no other options are available.

Figure 9.10. Defender.

Usually, the player is given a strictly limited number of smart bombs, and opportunities to replace them are either extremely rare or non-existent. The function of the smart bomb is to clear the area immediately surrounding the player of enemies. Usually, this means that the visible area is cleared entirely of enemies, but the range cleared does vary dependent on the game. Smart bombs should be used by the player only in dire emergencies when there are no other options available. The scarcity of availability is the primary mechanism available to enforce this.

Hyperspace

Hyperspace is another mechanism for getting the player out of trouble. However, unlike the smart bomb , the hyperspace design element is just as likely to land the avatar in an equally difficult situation as it is to get it to safety.

The first commonly known game to make use of the hyperspace element was Asteroids , shown in Figure 9.11. When the avatar was in immediate danger of being destroyed by an oncoming asteroid , the player could hit the hyperspace button, which would instantly move the player to another part of the screen. The amount of times the player can hyperspace is unlimited. This is because the usefulness of the hyperspace is balanced out by the chances that the avatar could appear in a worse situation than before. Hence, the choice of whether to use the hyperspace is tempered by the risks involved in doing so. Ironically, the more necessary it is to use it (the more debris of the playfield ), the more risk there is to the player.

Figure 9.11. Asteroids.

Waves

During a level, the enemies that confront the player's avatar can be introduced in a number of ways (generally called waves ). There are two common ways that this is achieved. The difference between these two methods is in how the enemies appear.

With the first method, the layout and scheduled appearance times of the enemies are (for the most part) pre-scripted. There are very little (if any) random materializations of enemies. This has been used in games from the original Space Invaders to more recent games such as Max Payne and many others. In these types of games, the points at which the enemies appear are predefined, and an integral part of the level design. Of course, once they do appear, they can either follow a previously scripted attack formation, or rely on their own AI to locate and attack the player.

The second way of approaching wave formation is to make the enemies materialize randomly . Usually, there is some sort of algorithm determining which sort of enemies will appear, in order to maintain some sort of smooth difficulty progression. Often, the location and type of the enemy is selected from a small pool of variants for the particular level, as defined by the designer.

With both methods, the general usage is as follows . Throughout a level, the enemies arrive in some sort of formation. These formations will vary in composition to include a selection of enemies appropriate to the current challenge level. As the game progresses further, the formation composition will include stronger enemies. In some cases, the earlier weaker enemies will be phased out of the line-up, because they will no longer provide an effective challenge to the player. The enemies increase in difficulty and numbers as the player progresses in an environment, reaching a peaked frenzy at the end of the level. After this point, the environment changes and the intensity reduces to the initial point or somewhere just a bit higher.

The Big Boss

A traditional staple of action games are the boss characters . In many games, the end of a group of themed levels is guarded by a large enemy ”the boss character ”who is significantly harder to fight than any of the previously encountered enemies.

Defeating the boss takes the player to a new set of levels, with a different theme. Boss characters often can't be hurt by normal methods and require a special attack method to be damaged. For example, they could be invincible at certain times (i.e., Piranha Plants in Super Mario Sunshine can be hurt only when their mouths are open) or can be hurt only by certain weapons.

Often, the boss character is themed after the environment (or vice versa). For example, the first set of levels in Parasol Stars are themed after musical instruments. The left side of Figure 9.12 shows the first boss, which is in keeping with the musical theme.

Figure 9.12. The first bosses in Parasol Stars and Rainbow Islands .

Another boss design element that is used fairly frequently is to use a much bigger and stronger version of an enemy that the player has already encountered. The right side of Figure 9.12 shows a classic example, taken from Rainbow Islands . The first set of levels are garden themed (with the enemies being mainly insects and birds). One of the first enemies encountered is a spider. The boss character is simply a much larger version of that spider. This enhances the gameplay by allowing the player to predict some of the boss behavior, and gives him a small advantage in knowing what to expect ”an advantage that would not be there if the boss was entirely unfamiliar, and the player had to learn his behavior from scratch.

Of course, many games aren't suited for such an unsubtle set of themed levels, but even so, the themed level and big boss are one of the mainstay design elements of action games. The pattern of a succession of levels increasing in difficulty and challenge to a climax with the boss, before starting again at a slightly lower difficulty level, is present in virtually every level-based action-based game today. This is shown in Figure 9.13.

Figure 9.13. The general progression of an action game.

Wildcard Enemies

In order to break up the predictability of predefined waves, many games use a randomly spawned wildcard enemy to provide a fresh challenge to the player, and break up the predictability of wave-based gameplay.

For example, the Atari game Asteroids has predictable waves because, once they have appeared, the movement of the asteroids are completely deterministic ”except at the instance where they are shot and break up into smaller asteroids. However, at random points during the wave, an enemy UFO appears and follows a non-deterministic path , shooting at the player.

Another example is the Galaxian dive-bombers that break away from the main body of the wave and swoop down on the player's avatar. Wildcard enemies are usually a completely different class of enemy from level bosses, in that they are normally mixed in with normal enemies, and behave in a somewhat random or unexpected way.

Locked Door and Key

The player encounters a locked door that requires a key to open it. The key (which is not necessarily a physical key) is hidden somewhere in the level, and must be found in order to open the door.

This is a common method used to partition levels, and to control the player's progress in order to manage the gameplay delivery. This particular design element is often strung together in a sequence of several overlapping instances, where a key is used to open a door to give access to another key, which in turn opens another door that the player encountered previously. Doom is a particularly good example of this.

This design element should be used with caution. If it is used too liberally, then it tends to make the gameplay feel clich d, tedious , and old-fashioned. However, it can be very effective if some originality is applied to the design element, specifically in terms of how you implement the door/key mechanism. Remember, it doesn't have to be a traditional door and key. That would be boring, and has been done too many times. A door and key are just a conceptual representation of a construct that requires an effort (the key) on the part of the player to pass an obstacle (the door). A slightly more creative example is the use of this design element in Grand Theft Auto III . To open up new cities for play, certain difficult missions must be completed first.

Monster Generators

Gauntlet (and its various sequels) was one of the first games to feature a monster generator. The concept of a monster generator is simple: It's an object that generates fresh enemies to confront the player.

The monster generator isn't always visible: for example, enemy spawn points in games such as Doom are not explicit objects. Instead, the monsters just appear out of thin air in a flash of green light ”usually out of the sight of the player.

The difference between the use of monster generators in Gauntlet and Doom is substantial. In Gauntlet , monster generators are an integral part of the gameplay ”destroy the monster generators, and no more monsters will appear. Hence, the player has two main strategies: Fight the monsters, or destroy the generator. In terms of survival, the dominant strategy is to destroy the monster generators before they can spawn too many monsters, but if players are aiming for the high score, then they may hold off on destroying the monster generator until they have boosted their scores sufficiently. You can see in this case that the monster generators are not only an integral part of the gameplay, but they can play a strategic role too.

In Doom , however, the monster generators are much more behind the scenes. All players know is that monsters are appearing ”they are not given the opportunity to destroy the generators to prevent this from happening. The only sensible strategy under these circumstances is to avoid or destroy the monsters, and get to the level exit as quickly as possible.

Monster generators ”whether represented by a physical object or not ”can have other attributes too. The most obvious of these is whether the generator will spawn an infinite number of monsters or just a limited amount before being spent. If the monster generator spawns infinitely, then you may want to consider the possibility of allowing the player to destroy it.

Another consideration is whether the monster generator will spawn only one type of enemy, or whether it has a range of enemies at its disposal. This can either be a static relationship or can be tied in with the difficulty level.

Dungeon Exits and Level Warps

The dungeon exit signifies a transition within the game. Usually, this transition involves progressing to a new level, or a new area within the current level. The dungeon exit design element often is used as a goal or sub-goal of the current level. In other cases, it is merely an enabler , allowing the player to move between different areas while she attempts to complete other goals.

The dungeon exit is usually guarded by enemies and/or is well-hidden. The strength of the guard force and the difficulty in locating an exit is usually in direct relationship to the benefits of locating it. A common variant on this element is to provide more than one exit to a certain level. One of these is the standard exit, which takes the player to the next level. The second is a warp exit, which will jump the player ahead several levels. This second exit (often visible when you find the first) is difficult to reach, and requires extra sacrifice on the part of the player. The reward is usually proportional to the level of sacrifice, and this particular variation has been used in many games ”from Defender: Stargate (allowing experienced players to warp ahead to the more challenging levels) to Gauntlet (where alternative exits would jump the player ahead by a few levels for the same reasons as Stargate ) to games such as Luigi's Mansion and the Super Mario series (where some levels have hidden exits that lead to secret areas). If there is a hidden exit, you may want to give the player a subtle clue. For example, in Super Mario World , levels with secret exits are shown as flashing red dots (rather than flashing yellow dots) on the world overview map.

Mini-Maps

As action games became more complex, the play area began to span multiple screens of action, although the player still needed to be aware of what was going on in the game-world not visible onscreen.

The solution to this was to place a small dynamically updated map or radar display in the status display. There are several common configurations used for this. The original configuration was used in Defender and showed the entire game world to the player. Another configuration does not show the entire game world to the player, merely showing a zoomed-out view of the area surrounding the player. Williams' Sinistar used this approach, augmented with a text status line to notify the player of important events occurring outside of the scanner range.

A third configuration that we'll mention here ”although it is used more often in other genres that are not so action oriented ”is to have the map build up as the player explores. Areas that the player has not yet visited do not show up on the map. When the player visits them, they are drawn, and the map remains in the same form and is not updated further until the player revisits the area.

Victory Conditions

Action games ”being among the first of the genres ”benefited well from the early experimental years of the industry. The plots and settings of the early action games were many and varied, usually very original, and with the amount of extraneous story kept to a minimum; consequently, the nature of the victory conditions were for the most part simple and clear. The vast majority of games have a clear set of victory conditions, which are made clear to the player from the outset. In some cases ”particularly in the case of action games ”these victory conditions are illusory. For example, the accompanying blurb for Space Invaders talks about the player saving the Earth from the evil alien invaders. However, as anyone who has played the game is aware, after you've saved the Earth from one wave of evil invaders, another appears to take their place. And so on, ad infinitum, with each wave getting faster and more aggressive , until the player is overwhelmed.

Case Study 9.1 A Flawed Victory Condition

In some games, the victory condition is a result of a bug that prevents the player from progressing any further. This is surprisingly common, due to the fact that the developers of such games usually didn't test that far into the game. The most well-known example of this is probably Pac-Man.

For years, people have been attempting to get a perfect score on Pac-Man . In July of 1999, Billy Mitchell of Fort Lauderdale, Florida scored a perfect 3,333,360 points on a Pac-Man machine in Weirs Beach, New Hampshire. The perfect score is achieved by playing for six hours, through 256 levels of Pac-Man , eating every pellet, power-pill, blue ghost, and piece of fruit on every single level, without dying once. After the 256th level, the game freezes .

When he stepped away from the game after beating it, he said "I never have to play that darn game again ".

What can be derived from this is the observation that action games generally have one or zero victory conditions. They are split into two broad classes: those that are possible to win, and those where it is possible only to attain the highest score. Most early action games were of the latter class ”mainly due to memory constraints. In later years, when the processing power and storage capabilities increased, developers began incorporating structured stories into their games ”and with stories, come endings. Games such as Golden Axe (shown in Figure 9.14) had definite endings where, after the defeat of the big bad end-of-game boss (in this case, Death Adder), the players' avatars lived happily ever after (until the inevitable sequel comes along, of course).

Figure 9.14. Golden Axe.

As such, action games are unusual because the victory conditions are either crystal clear and known to the player in advance, or completely non-existent, being wrapped in an amorphous goal that can never be attained, such as the previously mentioned Space Invaders . Finding something between these two extremes is rare, mainly because it pushes the game away from being a pure action game into another genre entirely.

Interaction Model

The primary model in action games is based purely on fast interactions ”hand-eye coordination and reaction speed. The ability to think quickly and analyze situations almost instantaneously is favored as well. The player is usually given direct control over a single avatar. In order to efficiently translate the player's intent into actions within the game, the control methods for action games are usually extremely simple. Even so, various action games have attempted to implement more complex control schemes. The success of these games depended on the lengths to which players were prepared to go to learn the system. Games that succeed in this are usually the games that set the standards for new genres. For example, the Doom and Quake modes of interaction for FPS games are pretty much ubiquitous nowadays. Similarly, the Super Mario 64 control system has become the de facto standard control system for most console-based 3D platform games.

Often, the ability to analyze the situation in a particular game is a learned process developed through playing that particular game. In some cases, the skills learned playing one game can be applied to other games, with varying levels of transferability. For example, the skills learned when playing Space Invaders can be transferred wholesale over to other games such as Galaxians and, to a lesser extent, Centipede. There are several levels to the nature of the skills developed by playing certain games, and these levels are linked to how domain-specific the skills are. For example, the skill of picking off the spider in Centipede is not that useful in many other action games. Conversely, the skill of navigating the player's avatar and picking off a target further up the screen is useful in a much wider range of games. Obviously, if similar games use similar control systems, then the cross-game transfer of these skills is that much easier.

Of course, the ability to analyze a complex play-situation instantaneously is of limited use if the player has poor hand-eye coordination and reaction times. Studies tend to be conflicted on whether games improve or reduce these attributes in regular players. Common sense seems to indicate that exercising a skill tends to improve it, but what the official line is on this matter depends on the flavor of this month's study.

Perspective

Action games, whether directly or indirectly, are intended to be played from the viewpoint of the avatar. This is obvious when it comes to 3D FPS games such as Quake . You are looking through the eyes of your character ”there's no other way to interpret it. Unfortunately, despite protests to the contrary, the FPS 3D view is probably one of the most unrealistic views possible. We do not dispute the aesthetics of this viewpoint ”in fact, we believe it is excellent for immersion in a game world, but in strictly purist terms, it is simply not realistic.

The average human has 120 degrees of vision and can detect movement in the peripheral field at up to 180 degrees laterally. The average game of Quake shows a 30-degree view ”not to mention the fact that your ability to control the character is solely provided via a keyboard/mouse interface. Compared to the freedom of view and subtle nuance of movement in the real world, in the game world, your avatar is a tunnel-visioned paraplegic in an electric wheelchair.

Some 3D games, such as Super Mario Sunshine , Max Payne , and the Tomb Raider series, offer a third-person view. The player can see her avatar onscreen. Aside from niggling issues with camera control, this is probably the closest perspective to natural vision. Players can see clearly ahead of them, and they also are provided with limited awareness of what is behind and to the side of them. The only fly in the ointment as far as this particular scheme goes is the camera. A good camera can make or break a third-person view game. If the player is to feel as if she is part of the action rather than a disjointed observer, then the camera must be as unobtrusive as possible. An obvious camera adds an extra degree of complexity for understanding the world ”another obstacle in the way of gameplay. Giving the player control of the camera is not a solution ”it's merely a quick patch of a broken feature.

For an action game, sometimes it's just not enough to give the player a view that is close to reality. In order to make the game manageable, it's necessary to give the player super-human vision. That sounds like a good justification for the 2D viewpoint, but really it is just a rationalization after the fact. 2D action games were often so frenetic simply because of the super-human viewpoint that they offered the player.

Humans are creatures capable of thinking in three dimensions. Hence, displaying a representation of a system in 2D instantly confers an advantage. There is an order of magnitude less complexity for the player to cope with in terms of object positioning. This means that 2D action games can afford to throw a lot more at the player before overwhelming them than an equivalent 3D game.

User Interface Design

In principle, user interface design for action games is extremely straightforward. It should follow the KISS (Keep It Simple, Stupid) principle to the letter. The user interface should be as minimalist as possible. In order for the player to be able to effectively play the game, he needs to able to accurately and quickly assess the play environment.

All the information that the player needs to be able to access in order to be effective at the game should be immediately present onscreen. Most action games require only a limited amount of information, so this isn't difficult to achieve. For example, the HUD (Heads-Up Display) for Quake III shows the minimum amount of information. Basically, it shows the player's current health, weapon, and amount of ammo. Don't try to show too much information to the player at one time. Not only does the player have to contend with the frantic action in the game, but he also has to pay attention to the indicators in the status panel. He should be able to do this at a glance, without having to work to interpret the information. Use simple schemes to get the required information across. One way you can do this is to use colors wherever possible to indicate changing situations, rather than textual or numerical methods. Another important situation to consider is when the player's attention needs to be attracted quickly to a changing status panel, especially when the panel is outside the main field of peripheral vision of the player; then he will be concentrating on the in-game action, not the status panel. If you need the player to notice something in the status panel, then you'll need to take appropriate measures. Within the main focus of view of the player, the eyes are sensitive to color and shape. Outside of this region, the eye is attuned to detect changes in contrast or color , so the easiest way to draw the attention of the player is to use a flashing or flickering indicator.

In some cases, additional information (too much to appear comfortably in one small status panel) is required. This should be avoided whenever possible, but when it is not possible to avoid, it must be handled carefully so as not to disrupt the flow of the game to the detriment of the player. If the player loses out by having to switch to a secondary map or status screen, then the enjoyment of the game is impacted. For example, in many FPS games, the level map is shown on a separate screen that obscures the main view. This means that the player has to be in a safe position to look at the map safely. Other games use a transparent overlay to display the same map information. Often, this is the ideal presentation method, as it allows the player to clearly see both the surrounding environment and the map. However, its effectiveness is limited if the map is so complex that it obscures the main view too much.

Another golden rule for action games is that the player avatar must be extremely easy to pick out. In the case of FPS games, this is easy ”the avatar is the player, looking out through the screen. This is the exception, however. In every other type of action game, the avatar is displayed onscreen. In almost all cases, the avatar looks unique ”it has a unique shape or position onscreen. However, the most effective way of ensuring that an avatar is easily discernable is use of color. For example, Lara Croft is the only entity onscreen in Tomb Raider wearing a light blue shirt. This means that if the player can see a splash of that particular light blue on the screen, then he is looking at Lara. This also means that Lara is immediately identifiable onscreen without any conscious thought process on the part of the player. In other games ”for example, in the case of two-dimensional scrolling games ”the avatar is often distinguished by position. It is always in the same absolute position ”or at least on the same horizontal or vertical line ”onscreen, and the world moves around it. This gives players a fixed point of reference about which to orient themselves .

Not only is it important to be able to pick out the avatar, but it is also extremely important to be able to quickly identify enemies. There are several mechanisms in use for this. The majority of action games use color schemes to achieve this. As mentioned previously, the avatar is often a unique color. An extension of this scheme is to ensure that enemies follow a common scheme of color or appearance. Think of the film Tron ”you can easily identify the bad guys because they're the ones in red. The good guys are in blue. This is a throwback to the old spaghetti westerns where the good guys wore white and the bad guys wore black. A similar scheme can also be used for collectible items. In fact, an often-used scheme is to have the avatar predominantly one color and all collectibles another color, with the majority of the background yet another color. Anything else is an enemy. Of course, this is mainly used in older games, and is often tied to hardware limitations (as in Pac-Man ). There is no reason to use this particular configuration, however, and it can be shuffled around, as long as it is consistent. For example, each level of Space Tripper uses unique color schemes for the enemies, collectibles, and avatar designed to have maximum contrast with the level scenery . In this way, it is easy for the player to analyze the playing environment as easily as possible. The only problem with this is the issue of color-blindness. Relying solely on color as a differentiating indicator excludes a significant section of potential game players. Use form and contrast in tandem with color to maximize the differentiation methods available to players. Of course, color blindness typically affects only 10% of males (and even fewer females), and usually only affects the ability to differentiate red from green (and dependent colors). Other colors (with little or no red/green component, such as shades of blue) are safe to use.

Action games (with one notable exception) require simple controls. Because of the fast-action nature of these games, the controls should, wherever possible, directly translate to avatar actions ”pushing left on the controls makes the avatar go left, pushing right makes the avatar go right, and so on. For 2D games, this is a fairly simple endeavor, but for first- or third-person 3D games, there is an additional complication caused by the third dimension. There will always be an extra level of indirection for the player to deal with, and the controls will not be as intuitive as a 2D game. Quake -style games, even though they have standardized on a fairly logically consistent control system, are by no means simple for a complete beginner. Learning to use the Quake -style interface is the biggest barrier to mass-market success for first-person 3D games. For example, consider the success of the Mario series of games on the early Nintendo console systems. Super Mario World on the SNES was a system-seller. On the strength of that game alone, Nintendo sold many SNES systems. However, the first 3D incarnation of the Mario series, Super Mario 64 , was not as immediately successful, even though the control system was as close to optimal as could be hoped. It was helped somewhat by the sheer eye- candy and novelty value, but for the average player, it was nowhere near as "pick up and play" as the earlier games, partially due to the added complexity of managing the camera as well as Mario.

The notable exception to the simple control systems mentioned previously is the specific sub-genre of fighting games. For these, moves such as walking, kicking, and punching are fairly straightforward to perform. But for the more complex and rewarding combo moves, those that can cause more damage to the opponent (and usually carry a correspondingly higher risk due to taking longer to perform), the player is expected to perform a long string of commands in the correct sequence in order to be able to pull off the advanced move.

At the other end of the spectrum are games in which the player's movements are directly emulated in the game. Without considering VR systems, a mass-market example of this is the arcade game Dance Dance Revolution . This is controlled by a set of footpads that the player has to dance upon in attempts to match the flashing icons that appear on the screen. Consequently, the player's avatar is controlled directly by the dancing (or more accurately, stomping) of the player.