FUNDAMENTALS OF GAME DESIGN, SECOND EDITION
Core Mechanics and Gameplay
Figure 10.1 shows that, during play, the core mechanics present challenges to the player and accept actions from the player, both mediated by the user interface. So far, our discussion has concentrated on the core mechanics as a description of a system, without addressing the role of the player. The core mechanics manage the gameplay of the game, implementing all player actions and many challenges. This section discusses how that works.
Challenges and the Core Mechanics
The core mechanics implement the mechanisms by which most challenges operate, and they perform tests to see whether a challenge has been surmounted. The challenges that the core mechanics present may appear at any level of the challenge hierarchy, from atomic challenges to the victory condition for the entire game. Remember that the level design actually specifies the type and placement of individual challenges for each level, but the core mechanics implement challenges, if necessary, when the player encounters them.
Suppose the level designers want to set up a purely static obstacle as a challenge, such as a wall that the avatar must climb over in an action game. You would not need to create an entity to represent the wall or a mechanic to present the challenge itself; the wall would simply be an unchanging feature of the landscape. The mechanics play a role in implementing the action the player takes to meet the challenge (climbing) but play no role in presenting the challenge itself. This type of challenge is called a passive challenge.
If the level designers need to detect that a player has conquered a passive challenge (in order to give a reward, perhaps), they design a special event that occurs when the avatar arrives on the other side of the wall—that is, when the avatar's location attributes meet a condition that the level designers establish. Otherwise, the player's presence on the other side implies success, which doesn't require any special mechanics.
Suppose that the level designers want to set up a more complex challenge for the player, such as a puzzle that the player manipulates to unlock a door. Your design for the core mechanics must supply the level designers with the necessary entities and mechanics to define the puzzle, allow the player to interact with it, display the consequences of her actions, and detect when the puzzle has reached its solution state. This is an active challenge.
An enemy character that the player must defeat in combat represents another active challenge. The core mechanics define the characteristics and the AI of the enemy character. The level designers place that character at a location in the landscape by setting his location attributes and perhaps they also set some other attributes, such as health and ammunition. In effect, your design creates the tools and parts that the level designers use to build levels, create puzzles, position enemies, and so on. In a long game, the level designers probably reuse the same tools several times to create variants of the same challenge in different parts of the game. (This is one of the reasons why the same characters seem to appear over and over in a game: The level designers reuse the basic mechanics.)
