oud

Harvey Smith - Orthogonal Unit Differentiation
gdc03_OUD.ppt

Bonus materials for our audience members at home, these terms were drawn from a bunch of sources, including my mentors, my enemies, others GDC talks, Ion Storm Austin Designer Pizza Lunches, late night pancake house rants, post D&D game rants and other school-of-nerd-life sources.

TERMINOLOGY and CONCEPTS

Abdication of Authorship
A general concept advocating more dramatic freedom for the player and less prescribed story. Games made with this concept in mind deliberately attempt to allow the player, rather than the developer, to author the narrative experience. Such games allow for player-driven actions that might seem "non-dramatic" in traditional storytelling terms, but are interesting and dramatic to the player because the player was responsible for the actions. Instead of saying, "In act two, the player must enter the throne room and attack the guards," a game in which the developer abdicates (as much) ownership of the narrative (as currently possible) would say, "In act two, the player is free to approach the throne room and handle the situation there in any number of ways" (even by taking a traditionally non-dramatic course of events, like standing around quietly and letting the guards walk past). In the first example, the events would probably be more interesting (and “cinematic”) to outside observers. In the second example, the events would probably be more interesting only to the player. (Goofy parallel: Slide show of the family vacation. Interesting to the people involved, but boring to the guests forced to watch the slides.) By tightly controlling authorship, developers are more likely to create dramatic and interesting traditional media, like an exciting flick. By abdicating authorship and providing the player with the information and tools to create his own media experience, developers might create a more powerful interactive experience for the player, made so because it is the player's own unique experience, the result of his own actions. The developer should always keep the player's desires in mind: What is it that the player wants to do? Does the player even want to go to the throne room? Maybe he doesn't; maybe he wants to do something else, skipping the throne room entirely.

Absolute Damage
When figuring up the amount of damage inflicted by an attack, it's not enough to simply set the damage value of a single attack. (Like, "Gun X subtracts 10 points of damage and gun Y subtracts 20.") The developer, for the purposes of balancing, must figure up the accuracy and rate of fire of the attack, so that he can know the average damage over a period of time. Then the developer can compare the 'absolute' damage of the attack to other attacks, using the same variables of damage per hit, accuracy and rate of fire. Often, gun X, over a 10 second period, for instance, will do less damage than the seemingly more powerful gun Y.

Affordance
A visual clue as to the function of a material or thing. An obvious indicator as to the (actual or perceived) properties of some material or object. For instance, the average person perceives a sheet of glass as a material through which to look. A vandal perceives a sheet of glass as a material for smashing. Swap out the glass with wood, and the average person perceives the wood as a material for blocking view or support (depending on the context). The vandal will probably not try to smash a sheet of wood, even if it is flimsy--instead the vandal will perceive the wood as a material for carving or painting graffiti. The affordance of the thing sets up psychological parameters for the person perceiving it. A slot is for putting things into, a button is for pushing, a knob is for twisting. Sometimes designs confuse people when the designer creates a function that is at odds with the affordance of the object. For instance, some car radios have knobs that (in addition to being something that can be twisted/turned by a user) can be pushed in or pulled out, which is not visible (or obvious) and therefore sometimes fails to work intuitively.

Agency
The amount of influence an entity has over itself, the game's environment or other entities. Often refers to the player's noticeable impact (i.e., "player agency") and the perception of that influence. According to Murray's book, Hamlet on the Holodeck, "Agency is the satisfying power to take meaningful action and see the results of our decisions and choices." The Bat, from the Atari 2600 cartridge game, Adventure, is a classic example of a non-player entity with agency.

Barrier to Entry
The inherent difficult most player's will experience in moving from learning the game to playing the game. A game's complexity level tends to make it more or less difficult to learn. The more complex the game, the greater the barrier to entry. The trade-offs must be considered: Does the increased complexity of a feature add game-play? Does it make the barrier to entry unreasonably high?

Blocking (or Non-blocking) Conversation
Information delivery (as with a conversation) that stops the player from otherwise moving through the world is considered "blocking." For instance, in Deus Ex, there are two forms for conversation: Either the player enters a 3rd person mode and loses interface control for moving around, or the player walks past an NPC who simple barks some voice line in a way that does not hinder the player's free movement through the world.

Complex System
A system that possesses or exhibits emergent complexity.

Embedded and Emergent Narrative
Narrative elements that are predefined could be called embedded. Narrative elements that emerge dynamically from the game could be called emergent. Example of embedded narrative elements: When the player reaches the end of hallway, a cut scene takes control of the game and plays out a small scene. Example of emergent narrative elements: In playing through a Quake deathmatch, one player shoots an enemy, jumps over a crate, falls into some acid and dies. This is a unique "story" created by the agency of the player.

Emergence
Properties that cannot be simply inferred from a system’s rules. Emergent behavior occurs when a system acts in an organized fashion beyond the sum capabilities of its individual parts.

False Choice
This occurs when the player is offered multiple choices, but only one is possible. Often the player is given choices, but no matter which option he chooses, the game dovetails into the one viable path. For instance, in Zelda, the player is offered the option of saying, "Yes" or "No" when the princess asks for help. If the player chooses "Yes," the princess thanks the player and the game continues. In the player chooses "No," the princess asks again, ad infinitum, until the player says, "Yes." If the player does not realize that the choice was a false one (because he chose the "right" choice initially, say), a false choice does not have a great negative impact. However, the player often tests the game and sees through this (smoke and mirrors) device, which leaves him disillusioned.

Feedback
Information communicating the state of the game to the player, usually in response to the player's actions. For instance, text appearing on the screen saying, "You are fatigued," is a an old-school way to communicate that the player is running short on 'endurance points' or something. Similarly, showing the player-character avatar suddenly breathing in a laborious fashion, bent over using an 'exhausted' animation, would be a more elegant form of the same feedback.

Feedback Loop, Positive
A means of de-stabilizing a system. Part of the output from a system is presented at its input in order to affect future output, increasing it. A positive feedback loop thermostat will warm the room as the temperature rises, and cool the room as the temperature lowers. In scoring systems, as one team pulls ahead, some disadvantage is conferred to the losing team, pushing the winners further ahead and (most likely) accelerating their victory. To use Marc LeBlanc's example: Guns on the back of the cars in a racing game represent a positive feedback loop; as the lead player pulls ahead, he fires back at the trailing players, putting them even further behind.

Feedback Loop, Negative
A means of stabilizing a system. Part of the output from a system is presented at its input in order to affect future output, decreasing it. A negative feedback loop thermostat will cool the room as the temperature rises, and warm the room as the temperature lowers. In scoring systems, as one team pulls ahead, some advantage is conferred to the losing team, pulling the losers along and (most likely) keeping the game "closer." To use Marc LeBlanc's example: Guns on the front of the cars in a racing game represent a negative feedback loop; as the trailing player falls behind, he fires ahead at the leading players, reducing the leading player's advantage.

Forced Failure
This occurs when the player is given a task that he cannot complete. For instance, if the game tells the player to "save the princess," but the embedded narrative events dictate that the princess dies no matter what the player does, this is a forced failure. Forced failure is a specialized form of false choice that results in punishing the player by making him fail.

Formal Abstract Design Tools
A set of conceptual rules, models and techniques for game design analysis. These should be well-defined and abstract (i.e., cross-genre). They should have day-to-day project utility, a well-understood application context and they should be 'lenses' not value statements.

Fun
The holy grail of games, but an ill-defined term for purposes of game analysis. Marc LeBlanc's GDC speech on complexity warns against the word "fun" being vague. He describes ways in which players often derive pleasure from games. (Subsequently, we've added to that list.)

Clearing: Many games allow the player to clean up a scattering of interactive elements. There’s a simple pleasure players seem to get from “Hoovering” their way across a room full of gold coins or revealing the blacked out sections of the maps in RTS games or RPG’s.

Collection: The act of accumulating things. (Could be referred to as Consumerism.) Sometimes tied to the desire to complete a set. Examples: Collecting coins in Mario. Collecting Magic cards. Buying things in The Sims.

Creation: Bringing something into existence. Building something that feels like it belongs to you. Examples: Constructing and growing a city in SimCity. Creating and arranging a fish tank in El-fish.

Discovery: Space to explore and gain mastery over. Sometimes conceptual space, like the rules to a new game. Examples: It's fun to range over a new (often blackened-out) map in many strategy games like Warcraft or Sacrifice. You can see players go through phases when playing successive games of Onhe Furcht und Adel--they gain enjoyment over discovering the parameters of the game (and the successful strategies therein), then mastering the game.

Diversion: Pleasure derived from performing routine game system activities--the mechanical act of manipulating the game. Examples: Playing an hour of Windows Solitaire.

Expectation: Waiting with exciting for some perceived reward or entertaining moment. Examples: The thrill of gambling; blindly waiting to see if you've 'won' playing slots. (DX1 featured a similar chest lock picking dynamic--the player spend a lock pick and waited for a few expectant seconds to see what he had won.)

Experience: Allowing the player to engage in a real-world activity that is beyond his practical means. Examples: Killing a person with a pistol. Flying a fighter plane in a flight sim. Driving crash-up derby cars in a mud arena car game. Getting to play against Tiger Woods in a golf match.

Expression: Self discovery/exploration. Identity expression. Examples: Choosing a self-gratifying nickname, character name or call sign in a game like Quake, EverQuest or X-Wing Vs Tie Fighter. Choosing a character race/group in an RPG that is identified with an archetype or demeanor. Deck construction in Magic the Gathering.

Fantasy: Vehicle for imaginative or impossible activity. Examples: Flying on the back of a red dragon. Battling the undead. Piloting a space ship.

Fellowship: Social aspects of gaming. Examples: Working with squad mates in FireTeam to form a plan and attempt to score a goal. Standing around, chatting in the town in Diablo.

Goal-completion: Being given a clear goal and actually recognizing that it has been accomplished. Example: Completing a bridge level in Bridge Builder. Completing a mission in C&C (in which the player is often given very clear goals, like, "Build at least 12 tanks.").

Investment: Spending time on some game element and thus coming to value it. Examples: Slowly building up a 60th level druid in EverQuest.

Media-migration: Players desire to interact with familiar (and often well-liked) fictional elements from other media. The keys to this are familiarity (with the established fiction) and interaction. For instance, during beta-testing of the Aliens vs. Predator game, players demanded the option of carrying and using Hicks' shotgun, even though it was an antiquated, inferior weapon. In Star Trek games, players get excited at the option of attempting their own solutions to classic problems/encounters posed by the television series. Using a light saber from Star Wars carries its own appeal.

Narrative: Drama that unfolds over time, creates tension, engages us. Examples: Learning of "Tommy and Rebecca's" situation in System Shock 2 and finally seeing them run down the hall toward escape. (Embedded narrative.) The dramatic events that occur in a Quake deathmatch as a result of the players' actions. (Emergent narrative.)

Obstacle: Encountering a challenge and overcoming it. Examples: Making a difficult jump in SSX.

Sensation: Aurally or visually pleasing aesthetics. Examples: The first time the player steps out onto a hill and overlooks the world in Sacrifice, with its amazing art, he is in sheer awe and feels pleasure.

Victory: Putting the beat-down on an opponent. Some people are driven to compete and gain pleasure from winning. Examples: Players love being the top-ranking player in a Quake deathmatch.

Intentionality
Player Intention is the ability of the player to devise his own meaningful goals through his understanding of the game dynamics and to formulate meaningful plans to achieve them using the information and resources provided by the game. The plan needs to devised by the player. If the player simply figures out the one method of solving a problem in the game, then he has merely solved a puzzle. Intentionality is therefore stronger in games that allow for emergent solutions, as opposed to pre-scripted solutions, devised the game's designer. Random or unpredictable behaviors are the enemy of intentionality.

Investment
Player investment is a sense of ownership or outlay on the part of the player that compels him to continue playing (or perhaps provides resistance against quitting). Investment can be based on the time and energy the player has put into the game experience, making him feel that he must continue playing to validate the effort (to make the outlay 'worth it'). Investment can also be based on the player's efforts self-expression, making him 'love' the aspect of the game he has altered according to his stylistic or strategic machinations. These forms of investment can manifest in multiple ways. In an RPG, the player may feel a sense of investment based on how powerful he has made his character (because it might have taken 40 hours of potentially repetitive action to reach his character's level of advancement). A player may feel a sense of investment in his skill at card games because of the years he has played and the skill he has acquired. In the other sense of the term, however, the player can also feel a sense of investment in a game that allows him to decorate a house. (See The Sims.) More subtly, the player may have a sense of investment in a game if he has controlled the narrative. (This may be one of the reasons that players like games with branches--the open-ended nature of such games allows the player control and makes the player feel like he owns some aspect of the experience.)

Immersion
A sense of being deeply absorbed, engaged and engrossed in a game. Using first-person perspective might be seen as a short-cut to immersion--players are already familiar with interacting from the first-person perspective. Using real world spaces might be seen as a short-cut to immersion--players are familiar with the real world, so making a game that evokes the real world creates a bridge between the player's personal experience and the game experience. Plausible settings with sound fictional integrity might contribute to creating a more immersive environment. [Rob Fermier’s GDC talk on the subject breaks down immersion into three components: completeness (the player can do what he expects to be able to do), realism (the illusion is never broken, the player is not jarred out of the game) and investment (the player cares about what happens). First-person-perspective games with realistic spatial representations take this a step further, adding a visual realism component; players immersed in first-person perspective games often physically dodge projectiles, lean in their seats when attempting to see around the corner.]

Micromanagement
In a games context, micromanagement refers to an activity that is 1) fundamentally simple, 2) low level, 3) could usually be handled by the game's AI and 4) often involves activities that players do not intrinsically enjoy. Example: Feeding party members in an RPG. It is simple, in that it involves simply activating a "feeding" feature. It is low level, in that it does not influence the overall game in a strategic way. It could be handled by the AI, so that when party members are hungry, they simply subtract food from the player's stores. It is not intrinsically fun or exciting, since it is a simple maintenance task that (as it is usually implemented) does not call for any self expression or strategic thinking.

Mid-level Game-play
Specifically within the context of the DX team, this has come to mean the following: Potential player interactions that are neither common/core enough to be called low-level or unique/story-based enough to be called high-level. Mid-level game-play generally refers to actions performed only a few times during the course of the game. These actions are composed of core actions that are performed many, many times during the game, but usually not to the same end. Ultimately, mid-level game-play actions accomplish some aspect of a mission arc. For instance, the player is told: "You must destroy SHODAN's ability to upload itself into the Earth computer database." This is a unique story arc within the game System Shock--it is performed only once. At the mid-level, it involves finding and disabling several in a set of satellite dishes. At a low-level, it involves planting an explosive on each dish. Planting an explosive is a core game-play action the player might do a hundred times or more through the course of the game. But it feels a bit different to be doing in the context of the high-and-mid-level goals. One of the best examples of mid-level game-play in DX1 was M02's rooftop sniper area. The player had to jump or climb from rooftop to rooftop in order to reach a warehouse. On each rooftop, there were snipers. The player was provided with sniper weapons and ammo. Although not all players chose to do this, many players had a great deal of fun jumping from one rooftop to the next, hiding in the shadows, taking up sniping positions and then zooming in/assassinating the rooftop guards. Yet, if you look at this, it was nothing new--jumping, hiding and using the sniper rifle were all actions performed many times by most DX1 players. In the context provided by the mission, however, these became a string of interactions representing good mid-level game-play.

High-level examples: A) Raid the MJ12 base. B) Scuttle the ship. C) Sneak into the police station to steal a computer file.

Mid-level examples: A) Blow up the rooftop power system to take down the MJ12 base security system down. B) Destroy the five critically weak weld points on the ship. C) Jump from rooftop to rooftop to bypass the patrolling police in the streets outside the station.

Low-level examples: A) Shoot some enemies. B) Plant some grenades. C) Pick a locked door, then use the computer to upload the file.

Narcissistic Effect
People want to be loved. They often enjoy being the center of attention. Single player games allow for this. Sometimes you can evoke a powerful emotional response in the player by catering to this need. For instance, the player walks his avatar into a room and an NPC looks up at him and says, "Good morning, sir." An even more compelling version of this involves imparting some information to the NPC regarding the player's agency, style and/or ethical choices; "Good morning, sir. I heard that you went in through the upstairs skylight last night and didn't set off a single alarm...you're pretty sneaky."

Orthogonal
A math term related to perpendicular axes (or right angled axes). Really useful, metaphorically, for discussing differentiation (or making elements "non-overlapping"). For instance: Units A are B are both cavalry troops--identical except for a slight difference in movement speed. While units C and D are different along orthogonal axes--C is a 'chuck wagon' troop that allows other units to have their food consumption needs met, and D is a pony express unit that can deliver messages from one commander unit to another. While units A and B have roughly the same features and are only different by degrees, units C and D have completely different features. The latter differences could be metaphorically summed up as being more "perpendicular."

Note: Some developers use “orthogonal” to describe a top-down ¾ sort of viewpoint for some games. From a map architecture standpoint, we always push for “non-orthogonal” shapes. From a unit/feature differentiation standpoint, we talk in terms of wanting things defined along “orthogonal” axes. So the term is somewhat overloaded.

Overloading
If a specific interface device (like a mouse button) or game object (like a corpse) has multiple functions or can be used in multiple ways, it is overloaded. For instance, in DX1, sometimes frobbing a body "searched" it for inventory items, and at other times frobbing a body "picked it up," allowing the player to carry it. The body was thus overloaded, which caused periodic problems when the player wanted to pick up a body, but could not because his own inventory was full. In general, a better design features a device or object with only one intuitive form of interaction.

Partial Failure
Randy Smith’s GDC talk on Analogue Structures mentions partial failure as a (potentially) more interesting condition for the player. Examples abound: A killing shot delivered by a sniper enemy to the player is a total failure. A wounding shot is a partial failure and allows the player to reaction, recover, plan, et cetera. The latter is more interesting, generally and judgmentally speaking.

Player Imperative
A need driving the player's high level course of action through the game, as established by the context of the game (or the game's fiction). Used often in a game with heavier fictional elements (like a strong sense of character or setting). Problems can occur if the imperative 'works' fictionally as a motive for the character, but not the player. For instance, if the character is Bill Clinton with the imperative to "kill all Republicans," but the player is a huge fan of Newt Gingrich, the player might find his imperative (or over-arching motive within the game) dissatisfying. "Stay alive and fight your way to the exit" (as used by games like Doom) is a universal imperative that all players will accept, but it lacks the power of a more complex dramatic imperative.

Possibility Space
The scope of possible actions or outcomes in a (game) space of supported interactions, both obvious and emergent. The larger the number of interacting elements, generally, the larger the possibility space. In Tetris, the possibility space covers all the places where you could decide to place your current piece, within the allocated time. In chess, the possibility space is any of the potential moves you could make, as defined dynamically by your past moves and the past moves of your opponent. In a typical FPS, the possibility space is mostly covered by your decisions about where to run, where and when to fire, and what power-ups to try and acquire and in what order. Detailed simulation systems often dramatically increase the possibility space in a game. For instance, in earlier games, the enemy awareness model often only took into account enemy facing and player position, from overhead in a 2D world. In more recent games, the enemy awareness model might take into account enemy facing, player position, sound propagation, lighting level, et al. In the case of each system (say, the lighting model, for instance, the game could use a coarser or finer representation model: Some games might simply feature light and dark, as digital states. Games with larger possibility space might feature many thousands of shades of gray, where light is affected by factors such as radiosity, distance, weather, et cetera.) In real life, the possibility space is endlessly varied.

Resource Economy
An orderly system of regulating the distribution and uses of game resources--a system specifically conceived to further the goals of the design, sometimes used merely as a balancing tool (to "recharge" the player-character), but used at other times to require the player to think about strategic tradeoffs. Games like Doom gave the player small clumps of ammo and health after particularly tough combat areas to allow the player to recover from losses in terms of health points and remaining weapon shots. Such games also gave out addition ammo and health in secret areas to reward the player for searching/exploring. Games like System Shock applied a much more stringent approach, restricting the resources to a point that required the player to consider each shot fired. (System Shock went further by adding an analogue rock, paper-scissors model to ammo types vs. defense types, requiring even more strategic thought to the expenditure of ammo resources.) In DX1, the game generated and consumed (at the player's hand) some of the following resources: skill points, augmentation canisters, ammo, health, energy, lock picks/multitools, flares and explosives.

Unit Differentiation
The degree to which game units are different. Ideally, units should be designed with distinct properties that give them a unique role within a game's unit ecology. Many games feature a dozen units that are only differentiated by numbers (or degrees)--they have essentially the same basic functionality. For instance: Some game might feature 4 types of fighting units that use melee weapons to inflict damage and move along the ground--each of these units might only differ in artwork, name (fictional concept), sound effects, damage inflicted per attack, movement speed and health rating. A more interesting model--in which the development team employs a more orthogonal unit differentiation approach--might feature 4 units that have a completely different set of powers: Unit A floats along the ground (or over water) and can heal other units. Unit B is stationary and has the ability to increase the attack damage inflicted by any nearby ally units. Unit C can teleport to the corpse of any ally unit and can periodically convert enemy units into ally units. Lastly, unit B Unit D moves along the ground and can attack with melee weapons. (Sometimes referred to as "heterogeneous" unit design.)


EXPRESSIONS/CONCEPTS

Don't Break the Fiction
This is a term intended to promote internal consistency (of fiction, physics, game rules, interface, et cetera). Ideally, the game's setting has its own fictional integrity. That is, it is a sealed environment where only elements from that setting exist. (A setting can be fantastical, relative to the real world, yet can still have its own integrity and plausibility.) It might strain credibility if the player is walking through the world of Deus Ex and suddenly meets an aged Duke Nukem, begging for cash. While this might be funny to some players, it would also serve to break the player out of his suspension of disbelief; it’s a meta-joke and it would remind the player of another game, the real world itself, and the fact that the world of Deus Ex is just an artificial setting. Suspension of disbelief and plausibility seem to aid in making the environment more immersive. (In-jokes should not be recognizable to uninformed players.)

Do Not Teach By Death
“Teaching by Death” occurs in a game when the player is confronted with an obstacle that requires his failure or dying at least once in order to succeed in subsequent tries. Example: The player comes to a fork in the road. The left passage leads to his goal. The right passage instantly kills the player (because the floor is actually a pit trap). The player has no clear way of knowing that the right passage is lethal. Discovering this requires dying and reloading.

Hot and Cold Media
Marshall McLuhan emphasized a distinction between what he termed "hot" and "cold" media. He said that a photo is 'hotter' than a cartoon, for instance. His notion was that hot media is less open to interpretation in two ways: it has a higher 'bit per square inch' style fidelity (greater definition/resolution), and it is less interactive on the part of the user. McLuhan said, "...a hot medium allows for less participation than a cool one, as a lecture makes for less participation than a seminar, and a book for less than a dialog." The concept is clearly useful and interesting, but when defining specific media as hot or cold, one often runs into debate. For instance: A video game with photo-realistic graphics is hotter than a short story in one sense. The game might show a train station that is very clearly defined, visually and spatially, and is thus less open to interpretation than a train station described in the short story. However, in another sense, the video game is cooler than a short story in that the game allows the player more agency--it allows the player more interactive control of the narrative.

It's Better to Reward Than to Punish
People like systems of reward. If players understand the rules and the rules are fairly applied, players do not mind their opponents being rewarded (i.e., scoring) for completing some scoring task. However, people do not like being punished. In attempting to balance the game, we will avoid punishing the player as much as possible. At times (generally under severe circumstances), we will punish (as when we subtract health).

Minutes to Learn, Years to Master
The best games are based around simple concepts that can be learned easily, but which can be applied at an advanced strategic level by an expert player in complex ways that often take a long while to learn. Go is perhaps the best example of this.

Playing the HUD
Some games do not provide the player with sufficient in the primary game view. So in order to compensate, these game provide the player with a smaller, abstracted view of world (like a HUD "radar"). Such representations of the game are often "gamier," but provide feedback information that makes the game more intentional or easier to play. Often, playing these games boils down to watching the small representation more often than watching the primary game view. It’s generally better to move the information found in the HUD into the game view as elegantly as possible.

Randomness in Games
Game elements that are so unpredictable as to seem random to the player might pleasurably surprise the player or test his ability to deal with dynamic, non-deterministic situations. (As a gameplay element, this can be fun: Trying to hit the pop-up bank robbers in a shooting gallery, for instance.) However, seemingly random elements also detract from strategic planning; if the player has no way of pre-determining the consequences of his action (or inaction), or no way of predicting the outcome of a situation, then he cannot act according to a strategic plan.

Unpredictable game events that surprise the player and help in making the game a more dynamic experience are sometimes perceived as fun. For instance, in Tetris, the player has no way of determining which type of block will be falling next--this comes as a surprise, forcing the player to react rapidly to each new block as he tries to fit it into the game's 'floor' surface. In other cases, unpredictable game events frustrate the player, thwarting his plan-execution. For instance (to use Tetris again), the 'floor' always maintains the shape it was given by the player--the player can plan where to drop the newest block based on the floor, since he can predict how the new block and the floor will fit together. If the floor changed shape randomly, the player's efforts to seat new blocks would be thwarted.

Often, modern games make good use of deterministic and non-deterministic elements. For instance, the player might come upon what is obviously a trap, connected to an opaque door marked "Danger." If the trap and the danger door behave predictably and according to expectation, these elements allow the player to formulate a plan. If the player springs the trap and the door releases some un-guessed-at new horror, the player might feel a (pleasurable) sense of panic and might be forced to dynamically alter his plans. The player could predict that A) the trap was a trap, B) the door was connected to the trap and C) the door would release something detrimental if the trap was sprung, but the player had no information telling him what would emerge from the door and thus might have been pleasantly surprised.

Reward For Goal Accomplishment, Not Methodology
Imagine that the player is outside a locked room and given the goal of entering the room. There is a locked door leading into the room on the north wall and a window on the south wall of the room. So the player can either pick the lock on the north wall or climb up through the window on the south wall. To reward the player for the act of "lockpicking" (as some games have done), but not for the other method of entering the room is to encourage one style of play--one that favors lockpicking. (Similarly, to exclusively reward any other method for entering the room is to encourage that style of play.) To reward both methods of entering the room has two problems: 1) It requires more work, as an individual reward must be attached to each method of entering the room, and 2) it punishes the player who figures out some new, emergent strategy for entering the room by not providing a reward for this method. The optimum solution, from the DX perspective, is to reward the player for entering the room itself, regardless of how he entered. This does not favor a particular play-style, it only requires the placement of one reward and it equally rewards a successful emergent strategy (unforeseen by the designer).

Rock, Paper, Scissors
In this game, each unit has exactly one other unit against which it wins and one other unit against which it loses. There is no overlap. Each 'move' in the game is unique and specialized based on its function. Example: Archers defeat air units, air units defeat ground troops, ground troops defeat archers.

Sandwich Gameplay
This refers to gameplay featuring inordinately long intervals of time in a game during which the player is not actually engaged in playing the game, but is instead waiting for some event or process to transpire. Example: The player character has the ability to slowly regenerate damage. So, before entering the next dungeon, the player decides to go and make a sandwich in 'real life' while his character in the game heals up.

Simulations Vs Emulation
A simulation is actually trying to represent the way a system works with consistent rules that are universally applicable. An emulated event is not as likely to be predictable to the experienced player (unless he has played through the area), since it is not repeatable under laws or operating parameters within the context of the game. Once the player learns the rules, events in simulated systems can be predicted.

Example 01: In the (heavy-emulation) game NOLF, there is a combat encounter that allows the player to fight and kill sharks with a speargun. Later in the game, the player is trapped on a (retracting) bridge above a shark tank. If the player enters the water and attempts to kill the shark with his speargun, the shark is unaffected. (To get past the shark, the player must have earlier knocked a guard into the water--the shark will then attack the guard, allowing the player to move past.)

Example 02: In the game System Shock 2, one player reported (on the web) a combat encounter that is the result of the game's simulated environment. The player-character was out of ammo and fleeing a hostile mutant. The PC ran into a room and was attacked by a turret. The PC hid in a corner, protected from the turret fire, trying to decide what to do. The mutant moved closer, searching for the PC. The PC then used his telekinetic psi ability to pull an explosive barrel toward him from the other side of the room. As the barrel passed through the stream of turret fire, it exploded, destroying the turret and killing the mutant.