FUNDAMENTALS OF GAME DESIGN, SECOND EDITION

Creating a Difficulty Progression

In a balanced game, the perceived difficulty of challenges presented to the player either should not change or should rise, so the player feels that later challenges present greater difficulty than those at the beginning. (If a game becomes easier to play, players will definitely feel that the game is unbalanced.) In order to achieve this, you have to take into account the player's increasing in-game experience and build in appropriate increases in absolute difficulty. If you wish to, you can also build in increases in the power provided by the game. Figure 11.3 shows this pro­gression graphically. Notice the gap between the absolute and relative levels of difficulty. This gap represents power provided by the game to meet challenges, which widens steadily as the player gains power.

The gap between relative difficulty and perceived difficulty on the graph represents the player's increasing in-game experience as she plays. At the beginning of the game, the perceived difficulty exactly equals the relative difficulty because the player has no in-game experience at all. As time goes on, her perception changes as she gets more practice.

If the available power grows at exactly the same rate as the absolute difficulty goes up, the relative difficulty will be a flat line, as illustrated in Figure 11.4 (next page). In that case, a level 5 knight would find it exactly as hard to kill a level 5 troll in the middle of the game as a level 1 knight would find it to kill a level 1 troll at the beginning of the game. But relative difficulty should not be a flat line because when you factor in the player's increasing in-game experience, the per­ceived difficulty actually goes down—the game gets easier. Aim to increase the absolute difficulty of the challenges somewhat faster than you increase the avail­able power to meet them. The gap between absolute and relative difficulty widens only slowly.

WHEN PERCEIVED DIFFICULTY SHOULD NOT CHANGE

The perceived difficulty throughout the game should either remain flat or should rise.

In most games, it rises. For some players, however, it should remain flat or rise only very slowly. Young children and casual gamers have a lower tolerance for frustration than older and more hardcore players. Mobility-impaired players may not get as much benefit from increasing experience as fully able players in games with physical coordination challenges. If you are making a game specifically for these groups, try to keep the per­ceived difficulty level nearly flat throughout the course of the game.

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Even if the perceived difficulty of a game rises only slowly, you do want the player to feel he attains bigger and bigger accomplishments as he goes. To achieve this, you must take into account all the factors pertaining to difficulty already discussed. Use the following guidelines:

■ Increase the absolute difficulty of challenges over time.

■ Increase the power available to the player to meet those challenges at a some­what lower rate. (See the later section "Understanding Positive Feedback.")

■ Be sure the player doesn't gain experience so fast that challenges start to feel as if they're getting easier rather than harder. Space challenges so that their relative difficulty increases slightly faster than the in-game experience increases.

■ Play-test your game to look for any dramatic spikes or dips in the perceived diffi­culty of its challenges so you can iron them out. A sharp, unanticipated rise in the game's difficulty will discourage many players and may prevent them from finish­ing the game even if the difficulty quickly falls again.

■ Start each game level at a perceived difficulty somewhat lower than that at which the preceding level ended, and increase the difficulty during the course of each level as well. Each game level should also take a little longer to play through and have a slightly steeper rate of difficulty growth than the one before. A graph explains this process best; Figure 11.5 illustrates a game with only five levels. This

sawtooth shape creates good pacing over the course of the game. Chapter 12, "General Principles of Level Design," discusses pacing at greater length.

Do not introduce sudden difficulty jumps between the end of one level and the beginning of the next. There is a good chance the player saved the game after completing the previ­ous level and has not played it for some time, so she might have lost some of the benefit of her experience.