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Putting It All Together
This chapter has introduced some general frameworks for thinking about the experience of play: how rules become play, the core mechanic, and game inputs, outputs, and internal player mechanisms. In the PLAY schemas that follow, we take more specific approaches to understanding how a player occupies the space of a game during play. But before moving on, we would like to bring our ideas about the play of experience together in a final, detailed look at a particular digital game: Centipede. In the early arcade game Centipede, the player's input occurs though a trackball device and a single button for firing. The player uses the trackball to move a bug-like character on the screen, firing shots upward at a variety of objects. Player input in Centipede is very simple: move and fire. Output, in the form of a video screen and audio speakers, is typical for an arcade game. The resulting core mechanic is somewhat generic: shoot enemies to score points and avoid enemies to stay alive. Despite the seemingly simple elements that make up the core mechanic, the game design of Centipede engages the player on a number of levels.The following analysis of Centipede relies heavily on observations made by game designer Richard Rouse III in his book Game Design: Theory and Practice.[4] He devotes an entire chapter to Centipede, providing a rigorously detailed reading of the game's design. How does a player take action in Centipede? There are some wonderful restrictions designed into the game. The trackball itself was a novelty when Centipede was first released, and even today, the large ball promises tactile, fluid motion. Ironically, however, the player cannot move the character anywhere: movement is restricted to the bottom 20 percent of the screen. By limiting the character in this way, the game retains a tight structural focus. As in games such as Space Invaders and Breakout (other games where the player moves along the bottom of the screen), game objects occupy the rest of the space above the player. In Centipede, this space contains both inert obstacles like Breakout bricks, as well as descending enemies like the aliens of Space Invaders. Even though movement is limited, the fact that the player can maneuver a little bit in the vertical dimension increases strategic opportunities and gives the player a much greater sense of freedom than in games that limit movement to a single spatial dimension. Yet the freedom of movement is just enough: if the player was given access to the entire screen, the game enemies and obstacles (which are focused downward towards the player's narrow strip of free action), would not function as successfully. Centipede's shooting mechanism also places important restrictions on player action. The player can hold down the fire button for a continuous stream of shooting, but only one shot can appear on the screen at a time. Because objects can be very close to the player or very far away, timing shots becomes a focus of game play. Sometimes, a stream of rapid, short-range shots are necessary. However, a shot that goes all the way up to the top of the screen can waste a maddening amount of time, as a player impatiently waits to gain the ability to fire again. The result of this simple design decision (only one shot on the screen at once) forces players to manage their shots like a resource, greatly enriching the decision-making process of the player. What distinguishes Centipede's well-designed play from a more generic 2D shooter is what Rouse calls the "interconnectedness" of the elements that appear in the game. There are five basic game elements, apart from the player's unit:
Mushrooms are immobile objects that clutter up the screen. It takes four shots from the player to destroy a mushroom, each shot taking away a quarter of the mushroom.
Centipedes are multi-segmented creatures that descend from the top of the screen and move back and forth, descending toward the player. When a centipede hits a mushroom, it drops a row downward, toward the player, meaning that the more mushrooms there are onscreen, the more quickly the centipede will descend. If a centipede segment is shot, it turns into a mushroom, creating a game play loop in which the player is constantly trying to clear mushrooms from the screen in order to slow the cen-tipede's descent, but is also creating more mushrooms by shooting the centipede. When a player shoots a segment of a centipede that is not the head or tail, the centipede splits into two creatures, becoming a multiple threat.
Fleas descend in a straight line from the top of the screen, leaving behind a dense column of mushrooms in their wake. Fleas only appear when the number of mushrooms in the lower half of the screen is below a certain amount, ensuring that there will always be enough mushrooms to create a challenging playfield.
Spiders move in a zig-zag style near the bottom of the screen, directly threatening the player's unit. But spiders eat mushrooms, so the player always has to decide whether it is better to kill a spider right away or to let it eat mushrooms while risking a collision with it.
Scorpions cross the screen horizontally above the player, so they do not pose a direct threat. However, they poison any mushrooms they encounter. If a centipede hits a poisoned mushroom, it will immediately move directly downward toward the player.As a result it is best to remove poisoned mushrooms from the screen.
Each of the five elements plays a role in the game's tightly designed system. The experience of play, a composite of all of the decisions made by the player, emerges from the possibilities mapped out by this system. For example, it is best to keep the overall number of mushrooms low, because the more mushrooms that are on the screen, the more rapidly a centipede will descend and the more mushrooms a scorpion is likely to poison. The mushrooms at the top of the screen are particularly difficult to reach, because they are blocked by lower mushrooms, and the limitation on the player's rate of fire makes it difficult to rid the screen quickly of mushrooms that are far away. It is easier to clear mushrooms from the bottom of the screen, but if the player clears too many, a flea will descend, dropping mushrooms across the entire height of the screen, including the top, where they are difficult to clear. The player must carefully prune mushrooms from the field of play, while retaining just enough to keep the flea from appearing. As Rouse writes,"…each of the creatures in the game has a special, unique relationship to the mushrooms. It is the interplay of these relationships that creates the challenge for the player."[5] He cites many examples of this interplay: If the player kills the centipede too close to the top of the screen, it will leave a clump of mushrooms which are difficult to destroy at such a distance and which will cause future centipedes to reach the bottom of the screen at a greater speed. However, if the player waits until the centipede is at the bottom of the screen, the centipede is more likely to kill the player. With the mushrooms almost functioning as puzzle pieces, Centipede becomes something of a hybrid between an arcade shooter and a real-time puzzle game.[6]
In looking at the system of Centipede, it is striking to see how a simple set of rules generates complex play. More than just a complex formal system, such rules ramify into a particular experience, a set of relationships that give the player's actions meaning. Shoot this mushroom or that one? Kill the centipede at the top of the screen or the bottom? Let the spider eat mushrooms or not? Furthermore, Centipede is an action game: all of this rich decision making happens in an extremely compressed space of time, resulting in the blend of action-shooter and strategy-puzzle experience Rouse describes. But there's more. In his explication of the game, Rouse goes on to describe not just the basic relationships between game elements, but also how they create what he calls "escalating tension" over time. Centipede's design carefully orchestrates the experience of play, creating tension across many levels of the game at once. For example, there is an immediate sense of tension created through the way that the flea and the centipede respond to being hit:
The first time the flea is shot, it will accelerate its descent, only being destroyed by a second shot.
Hitting a central segment of the centipede creates two centipedes.
In both of these cases, the result of a shot helps the player by bringing an enemy closer to destruction, but also adds additional danger to the game. As the centipede descends toward the bottom of the screen, anxiety slowly builds up. If the centipede reaches the bottom, extra centipede heads appear, making things dangerously crowded. However, once a level is complete, the player gains a brief respite before the next level begins, a relief that only accentuates the escalating tension that will immediately follow. Tension also escalates across an entire game. As the game proceeds, more and more mushrooms crowd the game space, until the top of the screen is quite dense with them. Of course, this makes the game more difficult in several ways. Additionally, the creatures become more challenging as the game wears on: the centipede moves faster and eventually begins a level already split into several independent pieces; the spider travels more quickly and in a tighter pattern, making it more difficult to kill. Centipede creates overlapping rhythms of pressure and relief, frustration and achievement, whether in a single game moment, on an individual game level, or across the game as a whole. This is play: the experience of rules set in motion. Players experience this system: as blinking pixels on a screen, as sharp electronic sounds from a speaker, as sweaty fingers on a trackball and button, as lightning-fast strategic planning. Play culminates in a whirl of perceptions and emotions, thoughts and reflexes, inside the mind and through the body of the player. Too often, game designers forget that they are creating, above all, an experience of play. It is not enough to tell a story. It is not enough to create pretty pictures or use dazzling technology. A game designer creates an interactive system, a set of choices, an activity. When you are making a game, ask yourself fundamental questions: What is the player actually doing from moment to moment in the game? How are these moments connected in a larger trajectory of experience? How does the experience of play become meaningful? What, above all, is the play of the game? Although there are no easy answers to these questions, focusing on the play of a game's core mechanic is a good starting point for designing powerful player experiences. [4]Richard Rouse III, Game Design: Theory and Practice (Plano, TX: Word-ware Publishing, 2001), p. 68.[5]Ibid. p. 68.[6]Ibid. p. 68.
