FUNDAMENTALS OF GAME DESIGN, SECOND EDITION
Skill, Stress, and Absolute Difficulty
Chapter 11, "Game Balancing," addresses gameplay difficulty in detail, but this chapter introduces some important concepts because the terms involved come up in a discussion of different types of gameplay later in this chapter. While these are not industry standard terms, you should find them useful.
This chapter is concerned with controlling the absolute difficulty of the challenges that you will present to the player. Two different factors determine the absolute difficulty of a challenge: intrinsic skill required and stress. Chapter 11 addresses additional factors that affect the player's perceptions about how easy or hard the game is.
The intrinsic skill required by a challenge is defined as the level of skill needed to surmount the challenge if you give the player an unlimited amount of time in which to do it. You can compute the intrinsic skill required for a challenge by taking the conditions of the challenge and leaving out any element of time pressure. How you measure the skill level of a challenge varies with the type of challenge and can involve physical tasks, mental tasks, or both. Consider three examples:
■ An archer aiming at a target requires a certain level of skill to hit the target. It takes more skill to hit the target if you move the target farther away or make it smaller. The archer gets an unlimited amount of time to aim. Even if he takes more time, it does not change the skill required.
■ Sudoku puzzles printed in the newspaper often include a rating that indicates whether they are easy or hard to solve. The player may take as long as he wants to solve the puzzle, so the rating reflects an intrinsic quality of the puzzle—how many clues the player gets—rather than the effect of a time limit.
■ A trivia game requires the player to know certain factual knowledge. Some questions are about familiar facts and some are about obscure facts. The skill level required by a question doesn't change if you give the player more time to answer.
Some challenges must include time pressure by the way they are defined—a test of the player's reaction time, for example. A test of pure reaction time (hit the button when the light comes on) requires no intrinsic skill at all. The carnival game Whac - a-Mole is a real-world example.
If a challenge includes time pressure, a new factor comes into play: stress. Stress measures how a player perceives the effect of time pressure on his ability to meet a challenge requiring a given level of intrinsic skill. The shorter the time limit, the more stressful the situation. Succeeding in a stressful game requires both quick reflexes and a quick mind. The challenges of Tetris do not require a great deal of intrinsic skill—if the player had plenty of time to think about the task, it would be easy to keep the blocks from piling up—but Tetris is stressful because the player must complete the task under time pressure. Golf, on the other hand, demands skill without being stressful—at least, in the sense of heavy time pressure. It would be considerably more stressful if the rules imposed more time pressure.
Games often create physical stress on the player's body. Time pressure requires players to use their eyes and hands more quickly; it makes them stiffen their muscles, and it raises their heart rates and adrenaline levels. Many people love this sensation, but you should modulate the pacing of your game to give them time to rest. Chapter 12 discusses this in more detail in the section "Vary the Pacing."
